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LIBRARY OF THE 

UNIVERSITY OF ILLINOIS 

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Atlas of 

Illinois 

Resources 

Section I 



Water Kesources 

and 

Climate 



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UNIVERSITY OF ILLINOIS LIBRARY 

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Atlas of 

Illinois 

Resources 

Section I 



Water Kesources 

and 

Climate 



STATE OF ILLINOIS 

BOARD OF 

ECONOMIC DEVELOPMENT 

Governor Otto Kerner, 

Chairman 

Victor deGrazia. 

Executive Director 



Printed by Authority of 
the State of Illinois 
November. 1958 



CONTENTS 



Water Resources of Illinois 

Water Resources of Illinois 1 

Runoff and Stream Flow 4 

Seasonal Variations in the Hydrologic Cycle 4 

Mean Annual Runoff and Seasonal Variations in the Hydrologic Cycle 5 

Minimum Runoff 6 

Minimum Runoff, 6, 12, 18, 24-Month Periods 7 

Developed Surface Water Supplies and Potential Development 8 

Surface Water 9 

Sedimentation 10 

Reservoir Sedimentation Surveys 11 

Ground Water Geology 12 

Bedrock Geology 13 

Sand and Gravel Aquifers 14 

Sand and Gravel Aquifers and Recorded Pumpage 15 

Limestone Aquifers 16 

Limestone Aquifers and Recorded Pumpage 17 

Sandstone Aquifers 18 

Sandstone Aquifers and Recorded Pumpage 19 

Industrial Water Pumpage 20 

Industrial Water Pumpage 21 

Irrigation 22 

Irrigation Systems 23 

Mineral Quality of Illinois Waters 24 

Municipal Water Softening Plants 25 

Mineral Quality of Illinois Waters (continued) 26 

„...^.. Ground Water Hardness and Iron Content and Municipal Treatment 27 



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AvERAGE Annual and Monthly Precipitation 28 

Average Annual Precipitation 29 

Frequency of Annual Maximum and Minimum Precipitation 30 

Lowest and Highest Annual Precipitation Expected Once in 5 and 50 years .... 31 

Long-Period Precipitation 32 

Long-Period Record oj Annual Precipitation: St. Louis, Peoria, Chicago, 

and Cairo 33 

Snowfall 34 

Average Annual Snowfall 35 

Heavy Snowfall and Deep Snow Cover 36 

Occurrence of Icing Conditions 36 

Average Annual Days with Snow/all of 1 Inch or More and Average Annual 

Icing Conditions 37 

Thunderstorms, Hail, and Tornadoes 38 

Average Annual Thunderstorms and Hail and Tornado Occurrences 39 

Temperatures 40 

Mean January and July Temperatures 41 

Heating and Cooling Degree Days 42 

Average Annual Heating and Cooling Degree Days 43 

Growing Season 44 

Average Length of Growing Season 45 

Illinois Water Rights Law 46 

Major State Agencies Dealing with Water Supplies 49 

Selected Reference List of Documents Pertaining to Water Resources 50 

Glossary 52 

Index of Counties, Cities, and Towns 54 

Urban Population and Location 59 



Research Agency 

Illinois State Water Survey Division 

William C. Ackermann, Chief 
H. F. Smith, Coordinator 
Glenn E. Stout 
Stanley Changnon, Jr. 
T. E. Larson 
Gustavo Patino 
W.J. Roberts 
John B. Stall 

Further Research Contributors 



Robert E. Bergstrom 

Illinois State Geological Survey Division 
John E. Cribbet 

College of Law, University of Illinois 
John L. Page 

Department of Geography, University of Illinois 



Produced by 



Department of Geography, University of Illinois 

Joseph A. Russell, Head 

Fred W. Foster, Directing Consultant and Editor 

James A. Bier, Cartographer 

Gilbert H. Topp, Draftsman 



Produced for 

Division of Industrial Planning and Development, State of Illinois 



WATER RESOURCES OF ILLINOIS 



Illinois is a water excess state, which means this resource is available in excess of 
demand. In fact, the water available to the state is conservatively computed to be at 
least five times the present usage. 

Illinois is almost an island, in a sense being surrounded by fresh water. Along 
its western border flows the mighty Mississippi and to the south and east are the 
Ohio and Wabash. Lake Michigan lies to the northeast. This is far from all, for larger 
supplies are readily available within the state in the form of great rivers such as the 
Rock, the Illinois, and the Kaskaskia, as well as many smaller streams. Out of sight, 
but important as sources of water supply, are the ground waters in the soil and in the 
deep rock formations. 

Illinois' water resources are as large today as when this area was a wilderness, 
and so far as modern science can determine, they will be undiminished and constantly 
renewed by a great inflow of atmospheric moisture or water vapor in the air which 
averages 2000 billion gallons (bgd) per day. From this source of moisture the rather 
ineflScient processes of nature cause only about 5 percent to fall as rain or snow, yet 
this mere 5 jjercent averages 99 bgd for the state. Evaporation from land and water 
surfaces and the transpiration from growing plants have first call on this water; 
together they consume and return to the atmosphere about 76 bgd. Some 23 bgd of 
stream flow, including ground water, are available from within the state, which, when 
added to the minimum flow of record on the Mississippi and Ohio, as well as the 
present pumpage and diversion from Lake Michigan, brings the grand total mean 
daily surface and ground water supplies available to Illinois to 43 bgd. This is an im- 
mense amount of water — five times the present state usage and one-sixth of the water 
usage for all purposes in the entire United States. 

Of course, water is not uniformly available either in place, in time, or in quality. 
Variations of the water resource are in part due to the great north-south dimension 
of Illinois, since within this 385 miles of latitude there is variation with respect to 
storm tracks and in distance from the primary moisture source in the Gulf of Mexico. 
For these and other reasons, precipitation varies from about 46 inches per year in the 
Shawnee Hills of southern Illinois to 32 inches in the vicinity of Lake Michigan. Most 
of this larger precipitation in southern Illinois occurs in the winter season, and about 
5 percent of this falls as snow. In northern Illinois about 20 p>ercent of the winter pre- 
cipitation is snowfall. 

Runoflf in the form of stream flow varies arcally in much the same pattern as pre- 
cipitation, and if spread over the state would vary in depth from about 16 inches per 
year in the south to 8 inches in the north. The higher runoff" in southern Illinois in 
conjunction with more rolling or hilly land surface lends itself well to the develop- 
ment of surface water impoundments. Northern Illinois, on the other hand, is more 




HYDROLOGIC CYCLE 



fortunate in the generally available ground water in unconsolidated glacial material 
and in the deep rock formations. 

As is well known, rainfall and stream flow also vary in time. To an extent these 
variations are cyclic with the seasons of the year, but wide deviations from the aver- 
age trend are more the rule than the exception. In addition to the seasonal and day- 
to-day changes there are the occasional extended periods of excess or drought. The 
years 1952-1955 constituted such a period of extended drought, not only in Illinois 
but throughout much of the mid-continent. Once experienced, an extreme period of 
record such as this becomes an important guide to future engineering planning and 
design. This drought of 1952-1955 has been the subject of intensive study and it 
is estimated to have been of a severity which can be expected only once in about 80 
years. 

Water also varies widely in quality, and this has been and still is the subject of 
intensive study in Illinois through the analysis and correlation of thousands of water 
samples each year. Water does not exist in the chemically pure form of H2O, but 



contains dissolved and suspended material from both natural and man-made sources. 
Also, there is no universally ideal water quality for all purposes. Illinois waters are 
usually mineralized to a degree, are moderately hard, and may contain iron and 
various other substances. Two points are important in this regard: information on 
water quality is available; and chemical, physical, and bacteriological treatment 
methods are available to adjust any original element of natural water quality within 
desirable limits. 

Complete knowledge for the full and economic development of water resources 
requires far more than data on rainfall and stream flow. Even the list of closely re- 
lated physical factors is long. These include topographic and geologic maps for the 
location of dam sites, and rates of evaporation and sedimentation for the design of 
reservoirs. Water temperature data are of great importance since the largest single use 
for water in Illinois is for cooling purposes in industrial processes. Air temperature 
and wet bulb data are needed in the design of air conditioning equipment, another 
important use for water. 

Present and projected uses for water in Illinois are factors of importance in our 
water resources knowledge and are subjects of continuing study. Present use of water 
in Illinois by major user categories is approximately 6 bgd for thermal power stations, 
2 bgd for all other industrial applications, 1.4 bgd for municipal use, and smaller 
amounts for agricultural uses. These growing uses, which presently total some 9.5 
bgd, compare with a potential, useful resource of about 43 bgd. 

Much of the foregoing discussion on water availability, its character, and its 
present usage underlines the necessity for detailed water resources information ex- 
tending over many years and in adequate detail. In this regard Illinois is indeed 
fortunate, since its water resources have been under increasingly intense study since 
the creation of the State Water Survey in 1895. This agency, working with the State 
Geological Survey and other state agencies, has accumulated a wealth of information 
on the water resources of the state. It has been said that Illinois has better records on 
its water resources than any comparable area in the world, and this knowledge is vital 
to the effective development and utilization of the water and other natural resources 
of the state. 

The pages which follow contain a brief but factual summary of water resources, 
climate, and related data. Through reference to available documents given in the 
reference list or to the indicated state agencies dealing with water supplies, more de- 
tailed information can be obtained. The right to use water is contained in a discus- 
sion of Illinois water rights law. 



RUNOFF AND STREAM FLOW 

W. J. Roberts 

Natural surface flow of water is termed runoff. In Illinois, 23 billion gallons of 
the approxiinately 100 billion gallons of average daily precipitation eventually run 
off in streams. The performance of these streams is determined from the study of long 
periods of stream flow records; the State Water Survey and other agencies cooperate 
with the U.S. Geological Survey in obtaining continuous records at 161 stream gag- 
ing stations within or along the borders of the state. 

Stream flow is usually expressed in cubic feet per second. This value is some- 
times converted to cubic feet per second per square mile of drainage area, or to 
inches of runoflf. Inches of runoff represents the depth to which a drainage area would 
be covered if all the flow derived from it during a period of time were distributed uni- 
formly on its surface. This latter term is useful when comparing runoff with pre- 
cipitation. 

The map shows the distribution of mean annual runoff in Illinois as obtained 
by using the average data for 25 stations. Drainage basins for these stations reach into 
Wisconsin in two instances and into Indiana in one. A considerable variation in 
runoflf occurs within the state; it ranges from less than 8 inches in the west and north- 
east to more than 16 inches in the hill area of southern Illinois. 



SEASONAL VARIATIONS IN THE HYDROLOGIC CYCLE 

W. J. Roberts 

Precipitation continues in motion when it reaches the earth's surface. Its course 
depends upon the degree to which it is afl'ected by the processes of infiltration, evapo- 
ration, transpiration, percolation, underground travel and detention, and surface flow. 
The influences and natural interrelationships of these processes vary with the seasons. 
Their effects may be studied best by beginning with the quantitative data available 
for rainfall and runoff and then from this base calculating the eflfects of the less well 
measured processes of evaporation and transpiration. The illustration opposite is the 
graphical result of such a procedure. 

It demonstrates that water passes into storage during the spring and fall periods 
when the evaporation and transpiration rates are low. It shows how the rainfall de- 
ficiency of the warm months results in a lowering of ground water levels and a reduc- 
tion in soil moisture. During drought years the recovery of ground water levels and the 
resumption of normal stream flow from such deficiencies may be seriously delayed. 



MEAN ANNUAL RUNOFF 

20 to 40 -Year Records 
for 25 Stations 

Illinois State Water Survey 



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SEASONAL VARIATIONS 

IN THE HYDROLOGIC CYCLE 

Southern Illinois 
Illinois State Water Survey 



I Slot* Wol«f Sur«*v 



Jan. Feb. Mor. Apr. May June July Aug. Sept. Oct. Nov. Dec. 



MINIMUM RUNOFF 

W. J. Roberts 

Minimum runoff is measured in terms of minimum stream flow, and is usually ex- 
pressed in cubic feet per second at a specified location for the drainage area of the 
stream involved. Results may be stated in inches for comparison with rainfall data. 
The value in inches is determined by calculating the depth to which an area would 
be covered if the stream flow for a given period were uniformly distributed over its 
drainage basin. The minimum runoff record will reveal the least amount of water 
available during periods of low runoff and consequently will indicate the storage 
capacity necessary for water storage facilities to meet the demands during such periods 
of low runoff. 

Observations from stream-gaging stations are of limited use for design purposes 
until they have been collected for at least 20 years. Data may then be tabulated by 
months, for instance, and totals for various periods calculated. The lowest value for 
the entire period of record can then be determined and plotted on a watershed map. 
In order to map minimum runoff, data are entered in the center of each drainage 
area. Isolines are so drawn that each runoff value represents the mean of its watershed 
area. 

At the end of the 1952-1955 drought, a study applicable to central and southern 
Illinois revealed that this period had the lowest runoff of record. Maps were drawn of 
minimum runoff for periods of from six months to five years duration. They showed 
that runoff was less than 5 percent of normal for 20,000 square miles in southern 
Illinois during a one-year period and less than 25 percent of normal for approximately 
the same area during a two year period. Thus, many water supply reservoirs, already 
overtaxed by increased municipal and industrial demands, were virtually emptied by 
the balance of out-flow over in-flow during the drought years. 

The designers of new water supply reservoirs require a knowledge of all water- 
shed characteristics, including the size and shape of the drainage area, the soil types 
present, and slope relationships. A consideration of the values expressed by the mini- 
mum runoff map is also important in reaching proper design decisions. 



MINIMUM RUNOFF 

Lowest Q-Month Period on 
Record, August. 1953, to 
July, 1954, Inclusive 



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MINIMUM RUNOFF 

Lowest 6-Month Period 
on Record, August, 1953, 
to January, 1954, _/ 

Inclusive '^ \ 




Illinois Slate Water Survey 



MINIMUM RUNOFF 

Lowest 18-Month Period 
on Record, August h^-^ 
to December, 1954 
Inclusive 



DEVELOPED SURf#:E WATER SUPPLIES 
AND POTENTIAL DEVELOPMENT 

W. J. Koberts 

There are over 900 water bodies in Illinois which merit being classed as lakes or 
reservoirs; in addition there are thousands of farm ponds. They may be either natural 
or artificial, and range through lakes, impounding reservoirs, and sloughs. Natural 
lakes are associated with parts of the glaciated area in the very northern part of the 
state, particularly Lake County; these waters are used principally for recreation. 
Fortunately, ground water is available locally in amounts sufficient to meet the needs 
of municipal water systems and no cities or towns rely on surface water for their public 
supplies in this northern part of the state. 

The greatest use of the state's surface water is from rivers — the Mississippi, the 
Wabash, the Ohio— with the addition of the considerable supplies obtained from 
Lake Michigan. Rivers within the confines of the state, such as the Rock, the Illinois, 
the Kaskaskia, the Embarrass, and the Big Muddy, also make sizeable contributions 
of water. 

There are large reservoirs in central Illinois, such as Lake Springfield, Lake 
Bloomington, Lake Vermillion, and Lake Decatur, designed for surface water storage. 
These are primarily water supply reservoirs but they also provide opportunities for 
recreation. Population and industrial growth in the cities served by these facilities is 
increasing demands on the supplies to such an extent that the need for expanded 
storage capacities already is apparent. Centers such as Mattoon and Effingham, hard 
hit by the drought of the early 1950's, have already taken steps to improve their situa- 
tions by building new reservoirs. 

Nearly all the larger communities in the southern third of the state rely on im- 
pounding reservoirs for their municipal water supplies. Having outgrown their 
original facilities, many have built new reservoirs since World War II. Crab Orchard 
Lake, the state's largest impounding reservoir, covers 11 square miles and has a 
storage capacity of 67,320 acre-feet. Including other tributory reservoirs, completed 
or in the final stages of development, the total facility will eventually be able to pro- 
vide for a continuous draft of approximately 50 million gallons a day. 

A recent study of the potential water resources of the 17 southern Illinois counties 
presents a favorable picture for the future. Hydrologic data indicate that reservoir 
sites are available for the potential development of a storage capacity able to supply 
700 million gallons of water daily. 

Surface waters are present in abundance in Illinois. There are many good sites 
awaiting development. Storage facilities for recreational, municipal, and industrial 
use are constantly in development and it can be said with assurance that the physical 
potential exists for a vast water resource development in this state. 



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GROUND WATER GEOLOGY 

Robert E. Bergstrom 

Ground water in Illinois is usually obtained from deposits of sand and gravel 
in the glacial drift or from the limestone or sandstone formations of the underlying 
layered bedrock. In both cases, the occurrence of favorable supplies depends upon 
several factors, some relating to the source and physical character of the water itself 
and others to the requirements of the user. 

The availability of ground water is controlled mainly by the presence of earth 
materials that store and transmit water. These materials, called aquifers, vary greatly 
in water-yielding capacity and are distributed in uneven fashion throughout the 
state. Other earth materials such as silt, clay, and shale may contain abundant water 
in the minute pores between grains but they retard movement of the water to such an 
extent that it cannot flow freely into a well. 

Aquifers are replenished (recharged) by water that seeps directly into the ground 
from precipitation or from streams or lakes. The rate of recharge of an aquifer often 
determines whether ground water withdrawal can be maintained safely for a long 
period of time. 

The mineral and bacterial quality of the water itself aflfects the availability of 
favorable supplies. In general, ground water is more highly mineralized at greater 
depths. The result is that some aquifers yield potable water only where they are close 
to the land surface. 

In addition to natural factors, the requirements of the user affect the suitability 
of an area for ground water development. For example, where large supplies are re- 
quired, as for an industry, or where water of specific chemical quality or temperature 
is needed, only certain areas of the state may be considered favorable. 

The map on the facing page shows the distribution and water-yielding character- 
istics of the various bedrock formations below the glacial drift; the cross sections il- 
lustrate the vertical arrangement of the formations, including the glacial drift. 

Bedrock formations (Cambrian through Devonian) are favorable aquifers in the 
northern third of Illinois where potable supplies are obtained to depths of 1 500 feet or 
more. However, these formations dip southward to a much greater depth in south- 
central Illinois, where a troughlike structure, the Illinois Basin, is developed (cross 
section AA'). Here they contain salt water. 

The Mississippian, Devonian, and Silurian limestones, which are aquifers of 
small yield west of the Illinois River and at the southern tip of the state, also dip 
toward the Illinois Basin. Here they are overlain by Pennsylvanian rocks — mainly 
shale — in which only small scattered supplies of ground water are available. Most of 
the area covered by Pennsylvanian rocks is relatively unfavorable for obtaining 
ground water from the bedrock. 

12 



ILLINOIS RtVER 



BEDROCK 
GEOLOGY 

Generalized 

Illinois Stote Geological Survey 




BEDDOCK 
[ j TERTIARY ond CRETACEOUS: 

cm 

I I MISSISSIPPIAN: 

I I DEVONIAN ond SILURIAN: Wol«i 

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SAND AND GRAVEL AQUIFERS 

Robert E. Bergstrom and H. F. Smith 

Most of Illinois is mantled by unconsolidated deposits left by the glaciers that 
overrode the north-central United States during the "Ice Age." The greatest southern 
penetration of the ice in Illinois was about to Carbondale. The last great glacial ad- 
vance in the state reached as far south as Shelbyville and Mattoon and as far west as 
the Mississippi River north of Rock Island. 

Glacial ice sheets, moving outward from centers of snow accumulation in 
Canada, scraped up soil and rock debris, transported it southward, and eventually 
dropped it along the melting ice borders. Deposits related to glacial times are mainly 
of three types, as they exist today: till, outwash, and loess. Till is a mixture of un- 
sorted, silty, sandy, pebbly clay deposited directly from the ice. Sands, gravels, and 
silts spread by the meltwaters are termed outwash. Loess occurs on uplands as de- 
posits of wind-blown silt from the river flats. 

Outwash sands and gravels are one of the main sources of ground water in 
Illinois. Outwash was deposited mainly in valleys leading away from the ice fronts. 
Thus the valley systems that were in existence before and during glaciation are today 
excellent water-producing areas. In these sand and gravel-filled areas large quanti- 
ties of water are available from relatively shallow wells that are usually drilled to less 
than 300 feet. Some of the valley systems are occupied by streams today, among them 
the valleys of the Mississippi River, the Wabash River, the lower two-thirds of the 
Illinois River, and the Kaskaskia River. In these instances coarse deposits of outwash 
occur beneath recent river alluvium. 

Other valleys were completely buried or obliterated by glacial deposits and are 
known today only from drilling records. The Mahomet Valley of east-central Illinois 
is one of the most important and best known. The thick sand and gravel beds in this 
buried valley provide ground water for many municipal and industrial supplies. 

The upland areas between the valleys were not flooded with meltwater carrying 
outwash. Sand and gravel deposits are therefore less extensive and ground water con- 
ditions are accordingly less favorable. 

Because northeastern Illinois was covered by glaciers during several stages of the 
"Ice Age," the deposits here are thicker and more varied than in southern and west- 
ern parts of the state where only the earlier glacial deposits are present. In most of the 
northeast, moderate quantities of ground water can be secured from sand and gravel 
aquifers in the glacial drift. In the western and southern parts of the state, where the 
drift is thin and composed mainly of till and loess, little water can be secured from the 
drift except in the flood plains of the major streams. 



SAND AND GRAVEL 
AQUIFERS AND 
RECORDED PUMPAGE 

Illinois State Geological Survey 
Illinois State Water Survey 




LIMESTONE AQUIFERS 

Robert E. Bergstrom and H. F. Smith 

Wells in limestone and dolomite, the latter a limestonelike rock rich in mag- 
nesium, draw water mainly from openings in the rock— joints, fissure systems pro- 
duced by earth stresses, and channels opened and enlarged by water solution. These 
rocks are commonly too dense to yield much water from pore spaces as do sandstone 
and other granular deposits. Because the water-filled fissure systems are irregular in 
size and distribution, yields from closely spaced, similarly constructed wells in lime- 
stone and dolomite may be quite different. 

Particular attention to sanitary conditions is necessary in planning wells in a 
limestone or dolomite area. When either is the uppermost bedrock formation, whether 
exposed at the surface or overlain by thin glacial drift, there is danger of bacterial 
pollution entering the ground water reservoir. Quarries may be sources of such con- 
tamination. The openings provide little filtering or other purifying action, and pol- 
luted water may travel long distances. 

The Silurian dolomite, commonly called Silurian limestone, is a source of ground 
water in northeastern and northwestern Illinois as shown on the facing map. Many 
municipal and most domestic wells in Du Page County and southern Cook County 
are drilled into these rocks. These wells are usually less than 500 feet deep and yield 
from a few gallons to over 1000 gallons per minute. 

Ordovician dolomites and limestones, specifically the Galena-Platteville beds, 
are widely used as a water source in that part of northern Illinois where they occur 
directly below the glacial drift. Under these conditions they provide dependable, 
although only small-to-moderate, supplies. However, where they are overlain by the 
uppermost Ordovician shale formation (Maquoketa) they are usually poorly fissured 
and yield little ground water. 

Mississippian limestones (St. Louis and Keokuk-Burlington) are a source of 
ground water chiefly west of the Illinois River. Usually the yields are not more than 
10 to 20 gallons per minute. Wells in these formations are used mainly for domestic 
supplies. South and east of the Illinois River, water-yielding limestones containing 
potable water are generally absent, except in two small areas. In Douglas and Cham- 
paign Counties water-yielding Devonian and Silurian limestones occur below the 
glacial drift along the crest of a north-south arch in the bedrock. At the southern tip 
of the state, limestone wells are constructed in Mississippian, Devonian, and Silurian 
limestones along the south rim of the Illinois Basin. These wells range in capacity from 
less than 20 gallons to over 500 gallons per minute. 



LIMESTONE AQUIFERS 
AND RECORDED 
PUMPAGE 

Illinois Stole Geological Survey 
Illinois Stole Water Survey 




MISSISSIPPIAN 

DEVONIAN ond SILURIAN 

[MTTH ORDOVICIAN 



Recorded Pumpage in 
Gallons per Minute per Well 



cm HO 

I I 20 to 100 

h^'»- I 100 to 500 

o 

J Ov.r 500 

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SANDSTONE AQUIFERS 

Robert E. Bergstrom and H. F. Smith 

Ground water is obtained from sandstone in many parts of Illinois. The most 
favorable area is the northern fourth of the state, where large supplies are available 
from the thick, extensive Galesville and Mt. Simon sandstones of Cambrian age 
and the St. Peter sandstone of Ordovician age. 

The Cambrian and Ordovician sandstone aquifers, which are separated by about 
400 feet of less permeable beds, are near the surface in south-central Wisconsin and 
north-central Illinois. From these localities they dip southeastward and wells may 
be drilled to 2000 feet in tapping these rocks in the vicinity of Chicago. The Gales- 
ville sandstone is the most consistently permeable of the three aquifers and supplies 
water for high-capacity wells producing 300 to 1500 gallons per minute. 

The Cambrian and Ordovician sandstone aquifers are under artesian pressure — 
that is, water rises in a well above the top of the producing aquifer. Artesian con- 
ditions are a result of the aquifers being overlain by "tighter" beds which hold the 
water under pressure maintained by the head developed at the higher intake areas 
to the west and north. Many of the early wells drilled into the sandstones flowed at the 
surface; however, the artesian pressures receded as more and more high capacity 
wells were drilled. Today, water levels are over 500 feet below ground surface in a 
few places in northeastern Illinois. 

The water from the sandstones is highly mineralized east of the Des Plaines 
River and south of the Illinois River. The line A-A' on the map is approximately 
the southern limit of potable water (less than 1 500 parts per million total dissolved 
solids) in these sandstones. For lack of more suitable water supplies, wells are drilled 
locally to the sandstones a short distance south of this line (to B-B') . 

In the central and southern parts of the state thin sandstone beds in the Penn- 
sylvanian system yield small quantities of water, seldom more than 10 gallons per 
minute. Also, there are a few areas where Mississippian sandstones yield ground water 
along the southwestern border of the state. Wells in these sandstones have low capaci- 
ties, rarely exceeding 20 gallons per minute. 

18 



SANDSTONE AQUIFERS 
AND RECORDED 
PUMPAGE 

Illinois State Geological Survey 
Illinois Slate Woler Survey 




INDUSTRIAL WATER PUMPAGE 



w . J. ixuL'f I i: 



Industrial pumpage refers to water pumped by industry from private sources. 
There is some industrial pumpage in nearly every county in Illinois. However, 10 
industrial centers — Chicago, Joliet, the Fox Valley, La Salle, Rockford, Sterling, 
Rock Island, Peoria, Decatur, and East St. Louis — dominate the situation from the 
standpoint of volume. There are a few smaller areas where pumpage amounts to 
between 5 and 10 million gallons per day. Individual industries scattered within the 
state account for 90 million gallons of daily production. 

A total of approximately 1700 million gallons per day is pumped by 489 estab- 
lishments, either from their own wells or from private surface water sources. Of this 
total over 250 million gallons per day are pumped by 394 industries from ground 
water, while 95 establishments pump over 1450 million gallons of surface water daily. 

In addition to the private pumpage, industry buys approximately 350 million 
gallons of water per day from municipalities. If water used by hydroelectric gener- 
ating plants and steam generating electric plants is included, industry in Illinois re- 
quires more than eight billion gallons in day-to-day operations. 

Large as this total seems, it is very small compared to the amount of water avail- 
able from the streams, rivers, and ground water supplies of Illinois. The quantities 
of water needed for an increasing population and for industrial growth and expansion 
are present in amounts sufficient to meet all foreseeable future needs. 



3 1 


20 30 40 50 60 


70 


„„„„„.;,„„„„„ 


90 1 




Precipitation 99 Billion Gallons i 
1 i 1 1 ^ 


n 


Power 6 Billion Gallons 








1 


Industrial 2 Billion Gallons 








1 


Municipal 1.4 Billion Gallons 










Agriculture 0.13 Billion Gallons 
(half in irrigation) 









AVERAGE DAILY PRECIPITATION AND PUMPAGE 



20 



Illinois 

INDUSTRIAL 
WATER PUMPAGE 

Not Including Municipal Water 
Supplied to Industry 

Illinois State Water Survey 




IRRIGATION 

W. J. Roberts 

Supplemental irrigation has been practiced in Illinois for about 30 years. From 
a few systems operated in Kankakee County in 1925, the practice has spread to 
76 Illinois counties where in 1957 an estimated 338 separate systems could water 
approximately 16,500 acres. The accompanying distribution map of irrigation systems 
in Illinois shows the greatest concentration in Kankakee County. Here over 50 gladiola 
growers supplement rainfall with sprinkler systems that use water from wells. There 
are also isolated systems depending on wells in several other counties, including Cook, 
Lake, and Woodford. Many developments are located in the alluvial plains of the 
principal rivers; others make use of ponds, lakes, and streams. In Madison County 
18 wells have been put into operation in recent years to supply additional moisture 
for the high- value horse-radish crops. 

Adequate water supply is the principal locational factor in irrigation. Topography, 
soil type, crop to be grown, and the availability of labor are also important con- 
siderations. Many irrigation systems have been purchased for use in Illinois without 
thought for the large amount of water necessary for efficient operation. With the 
advent of light, portable pipe about 1950, many farmers invested heavily only to 
find that their water sources were dry at times of critical need. In recent years nearly 
all irrigation systems have been purchased only after thorough studies of water avail- 
ability. In Illinois, the State Water Survey and the State Geological Survey have 
data available on the quality and quantity of surface water and ground water for 
any part of the state. The University of Illinois College of Agriculture has prepared 
sprinkler system guides for surface irrigation. The Department of Agricultural En- 
gineering at the University has several circulars on irrigation available for distribu- 
tion and also conducts irrigation clinics for salesmen, engineers, and interested farmers. 

At present, the greatest returns from investment appear to be from growing 
high income crops. Normally the rainfall during the growing season plus water 
stored in the soil is adequate for soybeans and corn. Thus a considerable increase 
in crop output would be necessary to justify an investment in irrigation equipment 
for the major field crops. 

Present Illinois laws do not define the rights of land owners regarding use of 
water for irrigation. Local shortages and the ensuing competition for water have 
created difficulties in some cases. The prospective user of irrigation equipment in 
Illinois should, therefore, assess the availability of water sufficient for his purpose, 
the cost of supply, and the competitive aspects of the situation before selection of any 
specific location. 

22 



T' 



IRRIGATION SYSTEMS V^ h-^" 1 

Illinois State Woter Survey (f" 



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MINERAL QUALITY OF ILLINOIS WATERS 

T. E. Larson 

In the natural course of events, water is virtually an indestructible chemical 
compound. Although it exists in many forms and places, its availability in the free 
state — as atmospheric, surface, or ground water — is the primary concern of man. 
Beyond the universal necessity of water for survival, man's interests are directed 
toward having the right quality in the right amount at the right time. One aspect 
of fundamental interest, especially in our industrialized world, is the chemical con- 
tent of water. Any discussion of this subject revolves around surface and ground 
water supplies, as the amounts of chemicals in atmospheric moisture are so small 
they are seldom significant. 

Water comes close to being the universal solvent; certainly this is the case in 
its natural role. In its movement over and within the earth's surface, water dissolves 
or otherwise collects mineral and organic substances. The nature of this burden 
varies with time and place, and there is, from man's standpoint, no combination 
of substances that will suit every use. For today's mechanized society, the presence 
of dissolved or suspended substances may affect the utility' of water. In the past, 
industries often were located with respect to water of suitable quality. The great 
demands placed upon the resource largely preclude this possibility today, but methods 
now available can be used to modify or remove the dissolved and suspended com- 
ponents in water to the extent that any water can be made suitable for almost any 
purpose. Costs, however, may exceed the economic benefit, so the public and in- 
dustry alike are alert to this problem as new sources of water are developed and 
old sources expanded. 

Water in Illinois is usually mineralized to a degree, is hard, and may also con- 
tain either some form of iron or suspended matter. The qualities of the available 
supplies are such, however, that these substances can be successfully and economically 
removed if they prove undesirable. Surface and well waters of the state are similar 
in hardness and other mineral content. There are, naturally, significant exceptions. 
All public water supplies obtained from streams, lakes, and reservoirs are clarified 
and chlorinated as a basic treatment, supplemented with treatment for taste and 
odor control, and are frequently softened. 

In general, streams in the northern part of the state have an average dissolved 
mineral content of about 450 parts per million (ppm) and a hardness of about 400 
ppm. Values decrease to near 300 ppm mineral content and 250 ppm hardness in 
western and southern Illinois. The waters from Crab Orchard Lake in the extreme 
south are exceptionally low in mineral content and hardness, running 200 ppm and 
110 ppm respectively. 

Fifty-four of 288 municipalities of over 2000 population, drawing water from 
streams and wells, have installed water softening plants. In addition, the public 

24 



MUNICIPAL WATER 
SOFTENING PLANTS 

Illinois State Water Survey 




_.-L-L.V 






V'l BLOOMINGTON I J 
I 1 y 1 Rantuul ' 



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water supplies of 80 smaller communities receive softening treatment. Lake Michigan 
water, which supplies 57 communities in addition to Chicago, is noted separately, as 
its mineral content is uniformly at 150 ppm and its hardness 125 ppm. Large scale 
softening is not indicated. 

In Illinois, approximately 35 percent of the public ground water supplies have 
less than 0.4 ppm iron concentration, which is not sufficient to cause staining. In 
addition, 27 percent of the systems containing more than this amount have iron 
removal plants. All clarified surface water supplies are free of iron. Manganese is 
present in sufficient quantities to stain in about 5 percent of the public ground water 
supplies, and about one-half of these communities remove it by treatment. 

Stream temperatures, as a general rule, vary from 32° to 75° or 85° F. between 
winter and summer. Ground water on the other hand, shows no great temperature 
variations and those that occur are gradual changes associated with depth beneath 
the surface of the earth. Water from depths less than 300 feet in the northern part of the 
state varies from 48° to 54° F. With greater depths this value often increases and 
may rise as high as 62° or 64° F. at between 1600 and 2000 feet. In the south, water 
from depths of less than 300 feet may be between 55° and 60° F. West of the Illinois 
River and south of Rock Island, deep well waters from 1400 to 2400 feet may have 
temperatures as high as 72° to 76° F. 

Water is abundant in Illinois today, and is sufficient to serve a growing popula- 
tion and an expanding industry. It is also very important to know that these supplies 
are suited chemically and temperaturewise for most public and private uses. When 
this is not the case the qualities are such that water treatment is economically feasible. 
Perhaps a greater problem concerning our water supply is contamination by man. 
The waste materials he may add to water can be much more difficult to remove than 
nature's mineral and organic substances. 



36 



Ground Water 

WATER HARDNESS AND 

MUNICIPAL SOFTENING 



Wotar Mftened by 





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777 




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100 200 300 400 500 600 700 800 

Total Hordness (in ports per miltion) 



Illinois State Water Survey 






Number of Public 
Ground Water Supplit 























- 














































































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^^ 






Y////////i 





Ground Water 

IRON CONTENT AND 

MUNICIPAL REMOVAL 



Total Iron (in ports per million) 



AVERAGE ANNUAL AND MONTHLY PRECIPITATION 

Stanley Changnon, Jr. 

Precipitation in Illinois varies considerably in time and space. The annual 
average amount is lowest in northeastern Illinois near Lake Michigan, where it is 
less than 32 inches. The highest average annual precipitation, more than 46 inches, 
occurs in the hill region of southern Illinois. The precipitation which produces this 
annual excess of south over north occurs during the colder half-year (October through 
March). For the warmer half-year (April through September), the average precipita- 
tion varies only from 20 inches in the north to 24 inches in the south, while during 
the six colder months the precipitation varies from 12 inches in northern Illinois to 
23 inches in southern Illinois. 

Precipitation in Illinois is associated principally with the interaction of different 
air masses within the state. The nature of the continental type of climate allows fre- 
quent penetrations throughout the year of different types of air masses and their 
associated weather disturbances. These often produce rain or snow. The basic dif- 
ference between winter and summer precipitation is related to the character of the 
air masses. Relatively cold, dry air masses predominate in the winter, especially 
in the north, while relatively warm, moist air masses predominate in the summer. 
During the warmer months, the chmate throughout the state is much the same. This 
similarity in basic warm season conditions is in part expressed by the lack of a real 
variability in the average precipitation of the warmer half-year. Fifty-four percent of 
the annual precipitation in southern Illinois occurs during the crop-growing season, 
61 percent occurs during this period in central Illinois, and 64 percent in northern 
Illinois. 

During the colder half-year a striking north-south difference in climate exists. 
Although the southern Illinois winter is much colder than the summer, the tempera- 
tures are warm enough and the air sufficiently moist to produce thunderstorms 
and summer- type characteristics in the winter precipitation. However, in central and 
northern Illinois the predominating cold, dry continental air does not permit the 
development of heavy precipitation. 

The average annual number of days with measurable precipitation increases 
from west to east across the state from an average of 110 days per year in the west 
to an average of 120 days in the east. However, the average annual number of days 
with 0.25 of an inch or more increases from 38 in northern Illinois to 50 in the south. 
February is the month of lowest average monthly precipitation throughout most of 
the state. There is, however, a latitudinal distribution from south to north in the 
average maximum monthly rainfall. March and April are peak months in southern 
Illinois. May predominates in central Illinois and June has the highest average in 
the north. 

28 



Average Annual 
PRECIPITATION 

With Average Monthly Amounts 
at Selected Locations 



llinois State Water Survey 




FREQUENCY OF ANNUAL MAXIMUM 
AND MINIMUM PRECIPITATION 

Stanley Changnon, Jr. 

Due to the great variability in annual precipitation from year to year, the annual 
averages are not representative of the conditions that can be expected to occur in 
any particular year. To express this variability, the occurrence of the annual maximum 
and minimum precipitation amounts expected on an average of once in 5 and once 
in 50 years are shown on the accompanying maps. For example, the annual minimum 
precipitation may be 22 inches or lower once in 50 years in northeastern Illinois; 
in the same period, a single year low of 28 to 30 inches can be expected in southern 
Illinois. Likewise, the highest annual precipitation expected once in 50 years in 
southern Illinois is 74 or more inches, while the probable maximum is 44 inches or 
more in the extreme northeastern part of Illinois for the same span of time. 

Since 1950, "once in 50 years" extremes of precipitation have occurred in Il- 
linois. For instance, in 1957 Cairo received 72.98 inches, which was the wettest year 
in 86 years of record, and this was the second total since 1900 to exceed the 69.21 
inches expected to be equalled or exceeded once in 50 years, on the average, at this 
station. Similarly, Paris, with 63.90 inches in 1957, exceeded the "once in 50 years" 
expected amount of 51.28 inches for the first time in 57 years of record. 

Recent years have also provided precipitation totals that equaled or exceeded 
"once in 50 years" extremes of minimum precipitation. During the 1952-1955 drought 
in the southern half of Illinois several locations experienced extremely dry years. For 
instance, Mount Vernon had 27.50 inches in 1953. This was the second year since 
1901 with a total below 27.64 inches, the "once in 50 years" expected low at the 
station. 

Prolonged drought periods lasting one year or longer occur infrequently in 
Illinois and seldom affect the entire state. Furthermore, most droughts or rainfall 
deficiency periods which may occur can not seriously affect surface water supply 
sources if proper reservoir design is employed. 

30 



LOWEST ANNUAL 
PRECIPITATION 
EXPECTED 
Once in 5 Years 




Illinois State Woter Surve 



HIGHEST ANNUAL 
PRECIPITATION 
EXPECTED 
Once in 5 Years 



LONG'PERIOD PRECIPITATION 

John L. Kagc 

In the selection of weather stations to portray long-period precipitation in Illinois, 
the length of the available record, the continuity of the record, and the degree to 
which these represent various parts of the state were of primary concern. Cairo and 
Chicago would seem to raise no questions in meeting the above qualities. There is 
no station in Illinois which has precipitation records approaching the length and 
continuity of those from St. Louis, Missouri. This station can well represent the 
southwestern part of the state. Peoria has the only long and continuous record for 
the area north and west of Springfield. 

Neither for Illinois as a whole nor for any individual station is there a definite 
precipitation cycle over a period of years. Periods of varying length with relatively 
low, as well as relatively high, precipitation exist, but there is no periodicity. From 
1872 — the year for which all four stations first reported — through 1957 there have 
been 18 years when all stations had precipitation above the average. Only on one 
occasion did all four have precipitation above the average for as many as three con- 
secutive years: 1882, 1883, and 1884. Only on three other occasions did all stations 
have precipitation above the average for even two consecutive years. 

During 19 different years all stations had precipitation below the average, but 
only on one occasion was it below for as many as three consecutive years: 1899, 1900, 
and 1901. In 1955 and 1956 the precipitation was below average at all stations for 
the only other occasion with as many as two consecutive years. Cairo and Peoria 
have each had five consecutive years with precipitation above the average, while 
Chicago and St. Louis have each had six. Chicago's precipitation has been below 
average for no more than three consecutive years, Peoria for four, St. Louis for five, 
and Cairo for seven. For the four stations as a whole 1930 was driest, though this 
was not the driest year for any one of them, and 1957 the wettest, but actually the 
wettest only for Cairo. 

If there has been any permanent change in the amount of precipitation over 
the years, these four stations do not reveal it. If the record for each station is divided 
into quarters, certain facts appear. At Cairo the driest quarter of the record averages 
38.71 inches, the wettest 45.89 inches, while at Peoria the driest quarter averages 
34.84 inches and the wettest 34.96 inches, for the greatest and least departures. The 
percentage departure from normal for the driest and wettest year has been 63 and 
173 at Cairo, 60 and 180 at St. Louis, 66 and 153 at Peoria, and 67 and 139 at Chicago. 
The variation from year to year and the absence of any pattern for the state as a 
whole, or for individual stations, makes long-period forecasting on the basis of trends 
impossible as of now. However, if past records in any way reflect the future, it may 
be assumed that precipitation will continue to supply Illinois with water equal to 
the amount of the past. 

32 



Long-Period Record of 
ANNUAL PRECIPITATION 
St. Louis, Peoria, Chicago, 
and Cairo 



Peorio 34.90 il 

Chitooo 33.01 ir 



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SNOWFALL 

Stanley Changnon, Jr. 



The distribution of snowfall in Illinois is directly related to the normal north- 
south differences in the winter temperatures. Under conditions which bring on 
precipitation during the colder half-year, moisture which falls as snow in northern 
Illinois usually falls as rain in the southern part of the state. Northwestern Illinois 
is the area of maximum snowfall, receiving over 36 inches annually. This is nearly 
four times more than that normally falling in the extreme south. The location of this 
area of greatest snowfall is associated with cold, polar continental air which normally 
predominates northwest of Illinois during the winter season. Moderating temperatures 
related to differences in latitude are responsible for the decreasing average annual 
snowfall as one progresses southward. Local conditions and influences, of course, 
give rise to some irregularities in this pattern. 

January is the month of highest average snowfall in the north and in a small 
area in the extreme south. However, February is the peak month for the area bounded 
on the north by a line from Alton to Danville and on the south by an east-west line 
crossing the state not far north of Cairo. Northern Illinois stations show measurable 
amounts of snow for seven months of the year on the average, as compared to only 
four months on the average in the south. 



Record Maximum Snowfai 



Jan. Feb. Mar. 

Rockford 36.1 21.8 23.5 

Urbana 18.2 18.5 32.0 

Cairo 24.2 11.7 11.7 

Jan. Feb. Mar. 

Rockford T T T 

Urbana T T 

Cairo 



Apr. 


May June 


July Aug. 


Sept. 


Oct. 


Nov. 


Dec. 


Annual 


9.0 


1.5 T 





T 


5.0 


14.8 


26.5 


62.1 


8.0 


2.5 








2.5 


11.2 


18.0 


39.9 


1.6 


1.5 T 








2.0 


6.1 


22.7 


47.7 


Reco 


RD Minimum Snowfall 












Apr. 


May June 


July Aug. 


Sept. 


Oct. 


Nov. 


Dec. 


Annual 




















T 


8.8 




















T 


6.7 























0.4 




T = Trace 













34 



Illinois 

Induifriol Planning and D*»el 



Average Annual 
SNOWFALL 

With Average Monthly Amounts 
at Selected Locations 

MOLINE 




AVERAGE SNOWFALL 


In Inches 


j 


34.38 


1 


3034 


1 


24-30 


1 


22-24 


1 


18-22 




14-16 




10-14 




8-10 



HEAVY SNOWFALL AND DEEP SNOW COVER 



The average annual number of days with snowfalls of 1 inch or more varies 
from three in southern Illinois to thirteen in the northwestern part of the state. This 
northward increase is gradual throughout the southern half of Illinois, with Quincy 
and Urbana averaging only three more days per year than Cairo. However, north 
of a line from Quincy through Urbana — which is, incidentally, near the mean winter 
isotherm of 32° F. — the number of days increases quite rapidly. An average of nine 
days per year is reached at both Moline and Chicago. 

The occurrence of heavy snowstorms — those yielding 4 inches or more snowfall 
in less than 48 hours — also reveals the same south-to-north increase. In southern Illinois 
a snowfall of this magnitude can be expected once a year. In central Illinois such 
snowstorms occur from one to two times a year, while in the north the average oc- 
currences are between two and three a year. 

The number of days with 1 inch or more of snow on the ground also has a dis- 
tribution closely related to the north-south temperature pattern. On the average, 
over fifty days a year in northern Illinois have 1 inch or more of snow cover while 
only ten days a year have 1 inch or more of cover in southern Illinois. 



OCCURRENCE OF ICING CONDITIONS 



The distribution of the average annual number of days with icing conditions 
of sleet and glaze reveals an area of maximum occurrence in central Illinois. Glaze 
conditions occur in .areas with temperatures at or near 32° F., during precipitation 
periods. The latitudinal distribution of temperatures during the winter is such that 
near freezing circumstances prevail with greater frequency in central Illinois than 
elsewhere in the state. The winter temperatures in southern Illinois are generally 
too warm to result in many glaze conditions, while the temperatures in northern 
Illinois are generally too cold. 

The average annual occurrences of sleet vary only slightly from place to place 
in Illinois, with station averages ranging between five and seven days per year. Most 
of the variation in icing conditions relates to the glaze or freezing rain component, 
with areas of maximum development in central Illinois and near Lake Michigan. 



Average Annual 
Number of Days with 
SNOWFALL OF I INCH OR MORE 

And with Ground Snow Cover of 

Inch or More and 3 Inches or More 
at Selected Locations 



age Number of Days 


1 


13-U 




1213 




11.12 




10-11 


1 


9-10 




8-9 


1 


7-8 




4-7 




5-4 




4-5 




3-4 




Stote Water Survey 



THUNDERSTORMS, HAIL, AND TORNADOES 



The average annual frequency of thunderstorms in the Middle West decreases 
northward from the Gulf of Mexico. Storm activity in Illinois generally reflects this 
decrease with changing distance from the Gulf; there is an average annual occurrence 
of 58 thunderstorms in Cairo compared with 37 at Chicago. However, in western 
Illinois there is a northward increase in thunderstorms, as shown on the accompany- 
ing map, appearing primarily as an increase in the frequency of nocturnal thunder- 
storms, principally in August and September. June is the month of maximum thunder- 
storm occurrence throughout the state and January is the month when they are least 
in evidence. 

Thunderstorms are a large contributor to the total precipitation of the state. 
The percent of the normal annual precipitation derived from this source increases 
from 38 percent in northeastern Illinois to over 44 percent in the south and to above 
50 percent in the western section of the state. Thunderstorms make their greatest 
contribution to normal monthly rainfall during July, when 70 to 85 percent of the 
total is produced in this manner. Annual average thunderstorm precipitation is lowest 
in the northeast, where less than 13 inches fall, and highest in the south, where it 
measures over 19 inches. 

The average annual occurrences of hail in Illinois have a varied distribution, 
with areas of maximum frequency in the unglaciated hill region of the northwest, 
the hill region of the south, and the Springfield Plain area in the southwest. These 
areas are identified in terms of surface features, since hail occurrences are considered 
to be related to conditions of topography. Hail occurrences vary considerably from 
year to year throughout the state. May, with an average of eight days, is the month 
of maximum activity. April, averaging six days, and March, averaging five days, 
rank second and third highest. Hail activity on a single day is more likely to be wide- 
spread during March and April than in other months. 

The distribution of tornado occurrences for the 25-year period of 1927-1952 
shows great areal variation. Some small areas in southern Illinois had as many as 
nine and other areas in southeastern and northeastern Illinois experienced as few 
as one for this period. One belt of maximum activity extends from the southwestern 
peak area northeastward through the Champaign-Danville area, and another such area 
extends northwestward towards Moline. Over 70 percent of all tornadoes in Illinois 
occur during a four-month period, March-June, and March is the month of maximum 
tornado activity. 



Average Annual 

THUNDERSTORMS 

with Average Monthly Occurrences 
at Selected Locations 



I ■ ■-■•■i 36-40 
^■1 56-«0 







c:^ 




Average Annual 

HAIL OCCURRENCES 



Average Number 



TORNADO OCCURRENCES 
FOR 25 YEARS 

1927-1952 

Averoge Number 
of Occurrences 



E33< 



Sw4 
7or8 



Illinois State VVoter Survey 




TEMPERATURES 

Stanley Changnon, Jr. 

The continental climate of Illinois can be expected to exhibit extreme variations 
in temperature from day to day, month to month, and year to year. These variations 
will be considerably less, hov^ever, in the warmer half of the year than in the colder 
six-month period. While occasional spells of severe cold are a characteristic of southern 
Illinois winters, the climate during this season is basically milder here than in the rest 
of the state. Summers are commonly warm- to-hot and usually humid throughout 
Illinois. The annual mean temperature in northern Illinois is 48° F.; it is 60° F. in the 
south. An annual mean variation of 12 degrees exists, therefore, between these ex- 
tremes of the state. 

In July, the warmest month of the year, the mean monthly temperature in 
northern Illinois is 74° F. as compared to 80° F. for the southern part of the state. 
During January, the coldest month of the year, the mean for the extreme north is 
20° F. as contrasted with 37° F. in the south. The July difference in means, shown 
from the above, is 6 degrees, while the January difference is 17 degrees. 

The range in the mean monthly maximum temperatures and the mean monthly 
minimum temperatures also shows north-south variation, as will be noted from the 
data for selected stations on the map. However, it can be observed that a greater 
latitudinal difference exists between the mean monthly maximum values than be- 
tween the mean monthly minimum values. Only slight local irregularities affect the 
uniform east-west orientation of the isotherms in all months. 

The uniformity of temperatures over the state during the warmer half-year is 
indicated by the fact that an average of 28 to 30 days with a maximum temperature 
above 90° F. is recorded in northern Illinois, while 35 to 40 days above 90° F. are noted 
in southern Illinois. However, a greater areal variation in temperatures during the 
winter is reflected by the average number of days with minimum temperatures below 
0° F. These average 2 days in southern Illinois, 8 in central Illinois, and 12 in the 
north. 

40 




MEAN JULY TEMPERATURES 

Illinois State Woter Survey 



HEATING AND COOLING DEGREE DAYS 

Stanley Chaiign*:);,, ^i. 

Heating and cooling degree days are units designed for measuring heating and 
cooling requirements. Calculating limits of 65° and 75° F. were selected as points of 
reference in the temperature scale where heating or cooling are necessary to maintain 
comfort. For instance, where the daily mean temperature is below 65° F., heating is 
necessary to maintain conditions of comfort for normal activities in any type of 
roofed enclosure. The map presentation can be used to illustrate the need for con- 
siderably more cooling volume in air conditioning systems in southern Illinois than in 
the north. 

Heating degree days are computed directly from mean temperatures and, conse- 
quently, have a latitudinal distribution in Illinois. They are determined by sub- 
tracting the daily mean temperature from 65 degrees and counting every degree of 
difference as. one degree day. For instance, a day with a 54° F. mean temperature is 
counted as 11 degree days. A low number of degree days exists in southern Illinois, 
normally less than 4000 per year, while a high of over 7000 per year is recorded, on 
the average, for the extreme northwestern part of the state. Except for local irregulari- 
ties, the monthly distributions also reveal a south- to-north increase. January has the 
highest monthly averages and July has the lowest. No degree days are recorded for 
three months of the year, on the average, in southern Illinois. On the other hand, heat- 
ing degree days are reported for all months in the north. 

Cooling degree days also reveal a distinct latitudinal distribution in the state. 
However, the north-south range from 100 to 600 cooling degree days annually is 
greater percentagewise than the heating degree day range of from 4000 to 7000 over 
the same area. Cooling degree days are computed by subtracting 75 degrees from the 
daily mean temperature. Every degree of difference calculated on this basis is counted 
as a cooling degree day. July is the month with the most cooling degree days, while 
several of the colder months record no cooling degree days whatever. Cooling degree 
days are recorded, on the average, during five months of the year in northern Illinois 
and seven months of the year in the south. 



:ari... 



Average Annua 
HEATING DEGREE DAYS 

With Average Monthly Number 
at Selected Locations 

Illinois State Water Survey 




Average Annual 
COOLING DEGREE DAYS' 

With Average Monthly Number 
at Selected Locations 



Deoree Doy, 




Unltun 100 




100-200 




JOO-300 




300-400 




400-JOO 




SOO-600 




400-700 


•»~.ogt ol 


»» r—ri, o«»«./loh<,- 


;x~t!T.::;".';:7:r;jl''7s° 



GROWING SEASON 

Stanley Changnon, Jr. 

The average length of the growing season conforms to temperature distributions 
in Illinois with a north-to-south increase in the length of the period. However, the 
Mississippi, Wabash, and Illinois River valleys appear to influence the growing season 
pattern by increasing the length of the season along their courses, as may be noted on 
the map. 

The average length of the growing season is defined as the number of days be- 
tween the last average date of killing frost in the spring and the first average date of 
killing frost in the fall. Average dates for the fall frost vary from early October in 
northern Illinois to late October in the south. Average dates for the spring also show 
a latitudinal variation, but the north-to-south difference is greater at this period than 
in the fall. In southern Illinois, the end of March is normally the time of the last kill- 
ing frost, while the end of the first week in May is the comparable period for the last 
killing frost in the north. The local influence of Lake Michigan and the Chicago urban 
area cause the eastern portion of Cook County to have a slightly longer growing sea- 
son than the surrounding territory. 

Dates of killing frosts can vary considerably from year to year, thus producing 
growing seasons of varying lengths. For instance, at Springfield the average growing 
season is 187 days, but there has been a season with 138 days, the shortest on record, 
and one with 231 days, the longest on record. On the average, the earliest dates on 
record for killing frosts in the fall are 29 days before the average frost dates. In the 
spring, the latest dates of killing frost on record are, on the average, 31 days after the 
average dates of killing frost. 

The probabilities of the last killing frost of spring and the first killing frost of fall 
having occurred by particular dates are indicated for selected locations in the ac- 
companying tables. As an example, the last killing frost of spring will have occurred 
at Chicago by April 16 in 50 percent of the years. 

Chance of Last Killing Frost of Spring Having Occurred by a Particular Date 

Percent Chance 0% 25% 50% 75%o lOO^o 

Chicago Mar. 20 Apr. 6 Apr. 16 Apr. 22 May 23 

Peoria Mar. 28 Apr. 9 Apr. 15 Apr. 23 May 9 

Springfield Mar. 22 Apr. 3 Apr. 15 Apr. 16 May 25 

Mt. Vernon Mar. 20 Apr. 9 Apr. 16 Apr. 23 May 7 

Cairo Mar. 3 Mar. 17 Mar. 30 Apr. 7 Apr. 24 

Chance of First Killing Frost of Fall Having Occurred by a Particular Date 

Percent Chance 0% 25%o 50%o 75%o ^00% 

Chicago Sept. 25 Oct. 14 Oct. 21 Nov. 4 Nov. 24 

Peoria Sept. 26 Oct. 12 Oct. 20 Oct. 29 Nov. 12 

Springfield Sept. 26 Oct. 12 Oct. 19 Nov. 1 Nov. 23 

Mt. Vernon Sept. 15 Oct. 12 Oct. 22 Oct. 28 Nov. 10 

Cairo Sept. 30 Oct. 24 Oct. 29 Nov. 9 Nov. 27 

44 



I Planning and Devel 



Average Length of 
GROWING SEASON 

With Average Dates 
of Killing Frost 



Stote Water Survey 




of Days 


^ 


150140 
160170 
170-180 
180190 


Yfffffj, 


190-200 


B 


200-210 
210-220 


April 21 " 


Av.rag. doU o» 

lort hilling f,o.l 

-Av.rao. dol. o( 

fWsl liilling Iroo 


'Lu>.jJ L- 


J« " 'I* 



ILLINOIS WATER RIGHTS LAW 



The availability of water for industrial and other uses includes consideration 
of not only the presence or absence of water in an area but also of the permissive 
and restrictive water rights laws which govern the use of the water that does exist. 

In Western states extensive litigation and conflict over these questions has 
been brought about because of severe shortages of water. Illinois has been spared 
many of these difficulties in the past because the state has had an adequate supply 
of water. This bounty has led to a relatively meager set of water laws and many 
questions cannot be answered with authority. Nevertheless the implications for 
agricultural, industrial, and municipal development and economic growth inherent 
in these laws are obvious. The following is a brief summary of pertinent aspects 
of Illinois Water Rights Law. * 

American Water Law 

Although the modern scientist views water in terms of the hydrologic cycle 
and sees all aspects of water as part of a single pattern, the law, largely for historical 
reasons, has created artificial classifications for handling water disputes. Different 
rules have developed for water in natural watercourses (rivers, streams, and lakes), 
for diflfused surface water, and for ground water (really underground or subterranean 
water, called percolating water if it is not a well-defined underground stream) . 

The 31 Eastern states follow the riparian doctrine as to water in natural water- 
courses; the 17 Western states follow the prior appropriation doctrine. The former 
doctrine is based on the idea that the water can be used only by those individuals 
who own land bordering on the river, stream, or lake or by someone who has ob- 
tained permission from such owner. This means that water is treated, in essence, 
as a private property right, although each owner has only the use of the water rather 
than the absolute possessory right. The latter doctrine is based on ownership by 
the people or the state, with permission to use granted as a property right on the 
basis of priority in time. Both broad doctrines have various interpretations; thus, 
riparian rights may follow the reasonable use theory or the natural flow theory 
or a combination of the two. 

Ground water, too, is subject to varying legal theories. The Eastern states 
usually follow the English rule of absolute ownership by the surface owner, some 
carrying the rule so far that even malicious use by the owner is privileged. Others 
say the use must be reasonable and prohibit use away from the surface land if it 

*This statement is extracted from a 73-page report prepared on this topic by Professor John E. Cribbet for 
the Water Resources Committee of the Illinois State Chamber of Commerce, dated January 1958. The full report, 
available for $1.00 at the Illinois State Chamber of Commerce, 20 North Wacker Drive, Chicago, should be used 
by anyone to whom the use of vv-ater is of vital concern. 

4h 



unreasonably harms a neighboring owner. Many of the Western states have adopted 
some version of the appropriation doctrine even for ground water and California has 
developed a new concept, entitled the correlative rights doctrine. 

Diffused surface water, flowing off the land after rains or snow melt, has not 
raised any serious questions as to use and it is generally assumed that an owner 
can make any use he desires of water which falls on his own land. The major prob- 
lem here has been how to get rid of surface water, i.e., drainage. Again, various 
theories have evolved, the two principal ones being the common enemy rule and the 
civil law rule of Roman Law adapted to the American scene, in Illinois modified and 
augmented by a modern Drainage Code. 

Illinois Water Law— the Common Law 

Illinois is a strong common-law state, i.e., it is committed to the legal principles 
laid down by the English and early American judicial decisions. 

Water Rights Law Pertaining to Water in Natural Watercourses. The cases con- 
cerning water in natural watercourses have tended to deal with matters of pollution 
and diversion rather than consumption, but there are a sufficient number of decisions 
to form at least a working base. Illinois follows the common-law riparian rights 
doctrine as interpreted by both the natural flow and the reasonable use theories. It 
has expressly repudiated the doctrine of prior appropriation and has recognized the 
inadequacy of the natural flow theory as a test for all riparian rights. 

Under the riparian doctrine water uses are divided into natural and artificial 
uses. Natural uses represent needs that must be supplied if man is to e.xist — drinking 
purposes, household wants, and water for his cattle or stock. For such purposes 
a riparian owner may take all of the water he actually needs. On the other hand, 
artificial uses are those which supply the comfort and increase the prosperity of 
the landowner — such as irrigating lands or industrial applications. Water for arti- 
ficial uses must be on a reasonable basis and one owner can not deprive another 
of a proportionate use of the water for this purpose. In diversion cases the natural 
flow theory may still prevail, but for pollution and consumption the reasonable use 
test is more frequently used. The decisions distinguish between natural and arti- 
ficial uses of water and place both industrial and agricultural uses in the latter class 
but do not establish any priority between them. 

All water rights are recognized as vested property rights and the owner can not 
be deprived of them except by due process of law. This means that such rights must 
be bargained for like any other property interest or taken by condemnation pro- 
ceedings after due compensation is paid. Condemnation can take place only if the 
taker has the power of eminent domain. Municipalities are treated like any other 
riparian owner, except that they have the power to condemn. 

Water Rights Law Pertaining to Ground Water. The Illinois law of ground water 
rests on a single case decided in 1899 (Edwards v. Haeger) which places the state 



in the list of those following the English common law. In the basic case the court 
held that "Water which is the result of natural and ordinary percolation through the 
soil is part of the land itself and belongs absolutely to the owner of the land, and, 
in the absence of any grant, he may intercept or impede such underground per- 
colations, though the result be to interfere with the source of supply of springs or 
wells on adjoining premises." However, the owner may not maliciously injure his 
neighbor. In the proper case Illinois would probably modify this view by a doctrine 
of reasonable use. 

Illinois Water Law— Legislation 

The water legislation in Illinois is varied in scope. The bulk of the legislation 
relates to such matters as drainage, navigation, pollution, and sanitation; areas 
that have an indirect impact on the problems of water consumption. A few statutes 
have a direct bearing on consumption. 

Legal duties, powers, and functions are spread among a number of governmental 
units, from local districts to various departments of the state government. Details 
of such statutory law are available, but are beyond the scope of this summary. 

Use of Lake Michigan Water 

The law relating to the use of Lake Michigan water is not discussed here ex- 
cept as the normal doctrine of riparian rights applies to that body of water. This 
important subject is excluded because it involves not only local and state considera- 
tions but also interstate, federal, and international (United States and Canadian) 
policies and arguments. 



48 



MAJOR STATE AGENCIES DEALING WITH WATER SUPPLIES 



There are several state agencies which have major responsibilities for the investigation, 
development, and protection of water resources and the services of these agencies are available 
for consultation on many types of water problems. The agencies mentioned below are those 
with primary responsibilities in water resources, although there are other state agencies with 
an interest in water. 

Water Survey Division and Geological Survey Division of the Department of Registration and Education, 
Urbana, Illinois. The Water Survey studies many aspects of the nature and extent of the state's 
water resources, including ground water levels, precipitation, surface water supplies, stream 
gaging, and siltation of water impoundment reservoirs. Information on the mineral quality 
of water and engineering information about well yields and water levels can be secured from 
this source. The Geological Survey deals with the geological aspects of ground water supply. 
These two agencies work closely together and have a storehouse of information available 
to all interested persons on most aspects of local water supplies. 

Division of Waterways of the Department of Public Works and Buildings, Springfield, Illinois. This 
agency has general supervision of all public bodies of water in the state, including those lakes, 
streams, canals, and rivers not owned by private interests, municipal corporations, or the 
United States Government. It administers more than 50 laws and regulations which protect 
the public interests in these waters. It regulates construction in public waters, prevents ob- 
struction of navigation in navigable watercourses, supervises planning and construction of 
flood control works, operates moveable bridges over the Illinois waterway and makes general 
surveys and investigations of Illinois watercourses. 

Division of Sanitary Engineering of the Department of Public Health, Springfield, Illinois. Among other 
activities, this division acts in a supervisory capacity relative to the sanitary quality, mineral 
quality, and adequacy of proposed and existing public water supplies, treatment, and purifica- 
tion works. The division also supplies the technical staff for the administrative activities of the 
Sanitary Water Board. 

The Sanitary Water Bosurd is charged "to control, prevent, and abate pollution of the 
streams, lakes, ponds, and other surface and underground waters in the state. . . ." Among the 
functions of the board are: reviewing plans and specifications for proposed domestic and 
industrial waste treatment works operation, making necessary investigations and reports 
upon natural waters, and conducting all other activities pertinent to a successful stream 
sanitation and conservation program. 

Division of Oil and Gas of the Department of Mines and Minerals, Springfield, Illinois. This 
division has jurisdiction over pollution of land and water resulting from oil field operations 
and issues permits for rock water wells. 



SELECTED REFERENCE LIST OF DOCUMENTS 
PERTAINING TO WATER RESOURCES 



Public Ground-Water Supplies in Illinois. Bull. 40, 1950. 
New Public Ground-Water Supplies 1950-1957. Suppl. I, Bull. 40, 1958. 
Quality of Surface Waters in Illinois. Bull. 45, 1958. 
Rainfall Relations on Small Areas in Illinois. Bull. 44, 1957. 

1952-55 Illinois Drought with Special Reference to Impounding Reservoir Design. 
Bull. 43, 1955. 

Water and Land Resources of the Crab Orchard Lake Basin. With U.S. Fish and Wild- 
life Serv., U.S. Soil Conserv. Serv., Southern 111. Univ., 111. Agric. Experiment Sta. Bull. 
42, 1954. 

Ground Water in the Peoria Region. With 111. State Geol. Survey. Bull. 39, 1950. 
Causes and Effects of Sedimentation in Lake Decatur. With U.S. Soil Conserv. Serv., 
111. Agric. Experiment Sta. Bull. 37, 1947. 

Preliminary Data on Surface -Water Resources. Bull. 31, 1937. 
Potential Water Resources of Southern Illinois. Rep. Investigation 31, 1957. 
Trends in Residential Water Use. Rep. Investigation 30, 1956. 

Preliminary Investigation of Ground-Water Resources in the American Bottom in 
Madison and St. Clair Counties, Illinois. Rep. Investigation 17, 1953. 
Temperature and Turbidity of Some River Waters in Illinois. Rep. of Investigation 1, 
1948. 

High-Rate Recharge of Ground Water by Infiltration. Circ. 54, 1956. 
Evaporation Records in Illinois. Circ. 43, 1953. 

Mineral Content of Public Ground-Water Supplies in Illinois. Circ. 31, 1951. 
Chicago Area Water Supply. Circ. 29, 1950. 

Local Climatological Data for Rockford, Monmouth, Urbana, and Mount Vernon. With 
U.S. Weather Bureau. 1955. 



Physiographic Divisions of Illinois. Rep. Investigation 129, 1948. 

Water Wells for Farm Supply in Central and Eastern Illinois. Circ. 192, 1954. 

Ground Water Possibilities in Northeastern Illinois. Circ. 198, 1955. 

Ground Water in Northwestern Illinois. Circ. 207, 1956. 

Ground Water Geology in Southern Illinois, A Preliminary Geologic Report. Circ. 

212, 1956. 

Ground Water Geology in Western Illinois, North Part. Circ. 222, 1956. 

Ground Water Geology in South Central Illinois. Circ. 225, 1957. 

Ground Water Geology in Western Illinois, South Part. Circ. 232, 1957. 

Ground Water Geology in East Central Illinois. Circ. 248, 1958. 



Stream Flow Data of Illinois. With U.S. Geol. Survey, 1937. 
Unit Hydrographs in Illinois. With U.S. Geol. Survey, 1948. 



Water Supply Characteristics of Iminois Streams. With U.S. CJcol. Survey, 1950. 
Floods in Illinois: Magnitude and Frequency. With U.S. Geol. Survey, 1954. 
Flow Duration of Illinois Streams. With U.S. Geol. Survey, 1957. 



Climate of Illinois, Summary and Analysis of Long-Timc Weather Records. Bull. 532, 111. 

Agric. Experiment Sta., 1949. 

Illinois Water Use L.wv. Coll. of Agric. with U.S. Agric. Research Scrv. Res. rep. AERR19, 

1957. 



Water Supply Papers (referring to Illinois). 

Bibliography: Nos. 427, 563, 564, 565, 1492. 

Surface waters: Nos. 563, 564, 565 and 194, 239, 44, 1278, 1337, 1338, 1387. 

Stream measurements: Nos. 83, 98, 128, 171, 207, 245, 265, 285, 305, 325, 355, 385, 
405, 435, 455, 475, 505, 525, 545, 565, 585, 605, 625, 645, 665, 685, 700, 715, 730, 745, 760, 
785,805,825,855,875,895,925,975, 1005, 1035, 1055, 1085, 1115, 1145, 1175, 1278. 

Underground waters, artesian pressure: Nos. 908, 938, 946, 988, 1018, 1025, 1073, 1098, 
1128, 1158, 1167. 

Quality: Nos. 239, 1186. 

Southwestern Illinois: No. 164. 

Springs: Nos. 114, 164. 

Wells: Nos. 57, 114, 149, 164, 364, 946. 

Illinois Water Supply, A Report on the Water Resources oi Illinois. 1956. 
I LLiNOis Water Rights Law and What Should Be Done About It, A Research Report. 1958. 
Proceedings of a Statewide Conference on Local Water Supply Problems, Peoria, 
Illinois. 1957. 



Data on Public W.vrER Supplies in Incorporated Municipalities. Circ. N846, 1956. 



The Industrial Potential of Southern Illinois. Southern Illinois Univ., 1954. 

Statewide Conservation Lake Construction Program. 111. Department of Conserv, 1947. 

Water Quality and Flow Variations in the Ohio Rivkr, 1951-55. Ohio River Valley 

Sanitation Commission, 1957. 

Water U.se in the United States, 1900-1975. I'.S. Department of Conunerce, 1956. 

Report of the Illinois Water and Drouth Study Commission. 70th General A.sscmbly, 

1957. 

Story of the Metropolitan Sanitary Di.strict of Gre.vier Chic.\go. Metropolitan 

Sanitary District of Greater Chicago, 1956. 

Industrial Operations Under Extremes of Weather. Meteorological Mono., Vol. 2, 

No. 9, Am. Metcorol. Soc, May, 1957. 

Publications of llie U.S. Weather burc.in ami the U.S. (ieological Survey are among the 
major sources of reference consulted in the compilation of this atlas. 



GLOSSARY FOR WATER RESOURCES AND CLIMATE 



Acre-Foot. A term used in measuring the volume of water, equal to the quantity of water re- 
quired to cover an acre 1 foot in depth, or 43,560 cubic feet. 

Aquifer. A geologic formation that is water-bearing and which transmits water from one 
point to another. 

Artesian Aquifer. A soil or rock formation which is confined above and below and in which 
water is under pressure. 

Cubic Foot per Second. A unit of discharge for measurement of flowing liquid, equal to a flow 
of one cubic foot per second past a given section. Also called Second Foot. 
Dam. A barrier constructed across a water course for the purpose of (1) creating a reservoir, 
(2) diverting water from a conduit or channel, (3) creating a head which can be used to 
generate power, and (4) improving river navigability. 

Drainage. An area from which surface runoff is carried away by a single drainage system. 
Also called Watershed and Drainage Area. 

Drawdown. The change in surface elevation of a body of water as a result of the withdrawal 
of water. 

Flood. A relatively high flow as measured by either gage height or discharge quantity. 
Ground Water. Subsurface water occupying the zone of saturation. In a strict sense the term 
applies only to water below the water table. 

Hardness. A characteristic of water, chiefly due to the existence therein of the carbonates 
and sulfates and occasionally the nitrates and chlorides of calcium, iron, and magnesium. 
It is commonly computed from the amounts of calcium and magnesium in the water and 
expressed as equivalent calcium carbonate. 

Head. The vertical height of a water column or its equivalent pressure in other units. 
Hydrology. The applied science concerned with the waters of the earth — their occurrences, 
distribution, and circulation through the hydrologic cycle. 

Hydrologic Cycle. A complete cycle through which water passes, commencing as atmospheric 
water vapor, passing into liquid and solid form as precipitation, thence along or into the 
ground surface, and finally again returning to the atmosphere as water vapor by means of 
evaporation and transpiration. 

Impervious. A term applied to a material through which water cannot pass. It is also applied 
to material through which water passes with great difficulty. 

Intake. The surface area upon which water that eventually reaches an aquifer or ground 
water basin is initially absorbed. Also called Catchment Area. 
Irrigation. The artificial application of water to lands for agricultural purposes. 
Permeability. The property of the material which permits appreciable movement of water 
through it when saturated and actuated by hydrostatic pressure of a magnitude normally 
encountered in natural subsurface water. 

Reservoir. A pond, lake, tank, basin, or other space, either natural or created in whole or in 
part by the building of engineering structures, which is used for storage, regulation, and 
control of water. 



Sedimentation. The process of subsidence and deposition of suspended matter carried by water. 
It is usually due to a reduction of the velocity of water below the point where the suspended 
material can be transported. 

Till. Deposits of glacial drift laid down in place as the glacier melts. These deposits are 
unsorted and unstratified rock, flour, sand, pebbles, cobbles, and boulders. 
Transmissibility. The number of gallons of water a day that percolate under prevailing condi- 
tions through each square mile of water-bearing bed for each foot thickness of bed. 
Transpiration. A process by which plants dissipate water into the atmosphere from their 
leaves and other surfaces. 

Water-Bearing. A term, more or less relative, used to designate a formation that contains 
considerable ground water. It is usually applied to formations from which the ground water 
may be extracted by pumping, drainage, etc. 

^one oj Saturation. The zone below the water table in which pores of the soil are completely 
saturated with water. 



Colder HalJ-Tear. A period of six months including October, November, December, January, 
February, and March. 

Degree Days, Cooling. These units are used to give an index for cooling requirements and are 
computed for each day by subtracting 75 degrees from the daily mean temperature 
(Fahrenheit). 

Degree Days, Heating. These units are used to give an index for heating requirements and are 
computed for each day by subtracting the daily mean temperature from 65 degrees 
(Fahrenheit) . 

Glaze. Rain that falls in liquid form and freezes to objects on the ground. .-Mso known as 
freezing rain and often referred to as ice storms. 

Growing Season. This period is the number of days between the last spring date with a tempera- 
ture of 32° F. or lower and the first fall date with a temperature of 32° F. or lower. 
Isotherm. A line on the earth's surface joining points of the same temperature at a given time 
or for a given period. 

Mean Monthly Maximum Temperature. This is computed by adding all the daily maximum 
temperatures in the month and dividing this total by the number of days in the month. 
Mean Monthly Minimum Temperature. This is computed by adding all the daily minimum 
temperatures in the month and dividing this total by the number of days in the month. 
Mean Monthly Temperature. This is computed by adding the mean monthly maximum tem- 
perature and the mean monthly minimum temperature and dividing this total by two. 
Nocturnal Thunderstorms. Thunderstorms that occur at night. 

Precipitation. All water which falls to the earth's surface, including hail, snow, and sleet as 
well as rainfall. 

Sleet. Transparent grains of ice formed by raindrops freezing as they fall. 
Snow. White or transparent ice crystals, often in complex hexagonal forms. 
Warmer Hatf-Tear. A period of six months including April, May, June, July, August, and 
September. 



INDEX OF COUNTIES, CITIES, AND TOWNS 

Incorporated Cities and Towns with Populations of 1000 or more in 1950 



County 



Map 
Coordinate 



County 



Map 
Coordinate 



County 



Map 
Coordinate 



Map 

Coordinate 



Adams 


A-8 


Ford 


G-6 


Livingston 


G-5 


Randolph 


D-13 


Alexander 


E-16 


Franklin 


F-1 3 


Logan 


E-7 


Richland 


H-11 


Bond 


E-n 


Fulton 


D-6 


McDonough 


B-6 


Rock Island 


B-4 


Boone 


F-1 


Gallatin 


H-14 


McHenry 


G-1 


St. Clair 


D-12 


Brown 


B-8 


Greene 


C-10 


McLean 


F-6 


Saline 


G-1 4 


Bureau 


E-4 


Grundy 


G-4 


Macon 


F-8 


Sangamon 


E-9 


Calhoun 


B-10 


Hamilton 


G-13 


Macoupin 


D-10 


Schuyler 


C-7 


Carroll 


D-2 


Hancock 


A-7 


Madison 


D-11 


Scott 


C-9 


Cass 


C-8 


Hardin 


H-15 


Marion 


F-12 


Shelby 


G-10 


Champaign 


H-7 


Henderson 


B-5 


Marshall 


F-5 


Stark 


D-5 


Christian 


E-9 


Henry 


D-4 


Mason 


D-7 


Stephenson 


E-1 


Clark 


J-10 


Iroquois 


J-6 


Massac 


F-16 


Tazewell 


E-6 


Clay 


G-11 


Jackson 


E-14 


Menard 


D-8 


Union 


E-1 5 


Clinton 


E-12 


Jasper 


H-10 


Mercer 


B-4 


Vermilion 


J-7 


Coles 


H-9 


Jefferson 


F-1 3 


Monroe 


C-1 3 


Wabash 


J-12 


Cook 


J-2 


Jersey 


C-10 


Montgomery 


E-10 


Warren 


C-6 


Crawford 


J-" 


Jo Daviess 


C-1 


Morgan 


C-8 


Washington 


E-12 


Cumberland 


H-10 


Johnson 


F-1 5 


Moultrie 


G-9 


Wayne 


G-1 2 


DeKalb 


F-2 


Kane 


G-2 


Ogle 


E-2 


White 


H-1 3 


De Witt 


F-7 


Kankakee 


H-4 


Peoria 


D-5 


Whiteside 


D-3 


Douglas 


H-8 


Kendall 


G-3 


Perry 


E-13 


Will 


H-4 


Du Page 


H-2 


Knox 


C-5 


Piatt 


G-8 


Williamson 


F-14 


Edgar 


J-9 


Lake 


H-1 


Pike 


B-9 


Winnebago 


F-1 


Edwards 


H-12 


La Salle 


F-4 


Pope 


G-1 5 


Woodford 


F-5 


Effingham 


G-10 


Lawrence 


J-11 


Pulaski 


F-16 






Fayette 


F-10 


Lee 


E-3 


Putnam 


E-4 







CiTKs AND Towns 



Map 
Coordinate 



County 



Map 
Coordinat 



Population County 



Abington 


C-5 


3,330 


Knox 


Auburn 


D-9 


1,963 


Sangamon 


Albion * 


H-12 


2,287 


Edwards 


Aurora 


G-3 


50,576 


Kane 


Aledo* 


B-4 


2,919 


Mercer 


Harrington 


H-1 


4,209 


Cook-Lake 


Algonquin 


G-1 


1,223 


McHenry 


Barry 


B-9 


1,529 


Pike 


Alorton 


C-1 2 


2,547 


St. Clair 


Bartonville 


E-6 


2,437 


Peoria 


Alsip 


J-3 


1,228 


Cook 


Batavia 


G-2 


5,838 


Kane 


Altamont 


G-10 


1,580 


Effingham 


Beardstown 


C-8 


6,080 


Cass 


Alton 


C-11 


32,550 


Madison 


Beckemeyer 


E-12 


1,045 


Clinton 


Amboy 


E-3 


2,128 


Lee 


BellevUle* 


D-12 


32,721 


St. Clair 


Anna 


E-1 5 


4,380 


Union 


Bellevue 


E-6 


1,529 


Peoria 


Antioch 


H-1 


1,307 


Lake 


Bellwood 


H-2 


8,746 


Cook 


Areola 


G-9 


1,700 


Douglas 


Belvidere * 


F-1 


9,422 


Boone 


Arlington Hts. 


H-2 


8,768 


Cook 


Bement 


G-8 


1,459 


Piatt 


Arthur 


G-8 


1,573 


Douglas- 


Benld 


D-10 


2,093 


Macoupin 








Moultrie 


Bensenville 


H-2 


3,754 


Du Page 


Ashland 


D-8 


1,039 


Cass 


Benton * 


F-1 3 


7,848 


Franklin 


Assumption 


F-9 


1,466 


Christian 


Berkeley 


H-2 


1,882 


Cook 


Astoria 


C-7 


1,308 


Fulton 


Berwyn 


J-2 


51,280 


Cook 


Athens 


D-8 


1,048 


Menard 


Bethalto 


D-11 


2,115 


Madison 


Atlanta 


E-7 


1,331 


Logan 


Bloomington * 


F-6 


34,163 


McLean 


;/ 






*( 


County Seat 









Place 


.Uap 
CoordinaU 


Population 


County 


Placf 


Map 
Coordinate 


Population 


County 


Blue Island 


J-3 


17,622 


Cook 


Dallas City 


A-6 


1,275 


Hancock- 


Bourbonnais 


H-4 


1,598 


Kankakee 








Henderson 


Bradley 


H-4 


5,699 


Kankakee 


Danville * 


J-7 


37,864 


Vermilion 


Braidwood 


H-4 


1,485 


Will 


Decatur * 


F-8 


66,269 


Macon 


Breese 


E-12 


2,181 


Clinton 


Deerfield 


J-1 


3,288 


Lake 


Bridgeport 


J-11 


2,358 


Lawrence 


De Kalb 


G-2 


11,708 


De Kalb 


BridgeView 


J-3 


1,393 


Cook 


Delavan 


E-7 


1,248 


Tazewell 


Broadview 


H-2 


5,196 


Cook 


Depue 


E-4 


2,163 


Bureau 


Brookfield 


H-2 


15,472 


Cook 


Dcs Plaincs 


H-2 


14,994 


Cook 


Brooklyn 


C-12 


2,568 


St. Clair 


Divernon 


E-9 


1,013 


Sangamon 


Brookport 


G-16 


1,119 


Massac 


Dixmoor 


J-3 


1,327 


Cook 


Bunker Hill 


D-11 


1,238 


Macoupin 


Dixon * 


E-2 


11,523 


Lee 


Burnham 


J-3 


1,331 


Cook 


Dolton 


J-3 


5,558 


Cook 


Bushnell 


C-6 


3,317 


McDonough 


Downers Grove 


H-3 


11,886 


Du Page 


Byron 


E-1 


1,237 


Ogle 


Dupo 


C-12 


2,239 


St. Clair 


Cairo* 


F-16 


12,123 


Alexander 


Du Quoin 


E-14 


7,147 


Perry 


Calumet City 


J-3 


15,799 


Cook 


Dwight 


G-5 


2,843 


Livingston 


Calumet Park 


J-3 


2,500 


Cook 


EarlviUe 


F-3 


1,217 


La Salle 


Cambridge * 


C-4 


1,489 


Henry 


East Alton 


D-II 


7,290 


Madison 


Canton 


D-6 


11,927 


Fulton 


East Chicago Hts. 


J-3 


1,548 


Cook 


Carbondale 


F-I4 


10,921 


Jackson 


East Dubuque 


C-1 


1,697 


Jo Daviess 


Carlinville* 


D-10 


5,116 


Macoupin 


East Dundee 


H-2 


1,466 


Kane 


Carlyle* 


E-12 


2,669 


Clinton 


East Hazel Crest 


J-3 


1,066 


Cook 


Car mi* 


H-13 


5,574 


White 


East Moline 


C-3 


13,913 


Rock Island 


Carpentersvillc 


H-2 


1,523 


Kane 


East Peoria 


E-5 


8,698 


Tazewell 


Carrier Mills 


G-14 


2,252 


Saline 


East St. Louis 


C-12 


82,295 


St. Clair 


CarroUton • 


C-10 


2,437 


Greene 


Edwardsville * 


D-11 


8,776 


Madison 


Carter ville 


F-14 


2,716 


Williamson 


Effingham* 


G-10 


6,892 


Effingham 


Carthage* 


A-7 


3,214 


Hancock 


Eldorado 


G-14 


4,500 


Saline 


Casey 


H-10 


2,734 


Clark 


Elgin 


G-2 


44,223 


Cook-Kane 


Cascyville 


D-12 


1,209 


St. Clair 


Elmhurst 


H-2 


21,273 


Du Page 


Central City 


F-12 


1,231 


Marion 


Elmwood 


D.5 


1,613 


Peoria 


Centralia 


F-12 


13,863 


Clinton- 


Elmwood Park 


J-2 


18,801 


Cook 








Marion 


El Paso 


F-6 


1,818 


Woodford 


Ccrro Gordo 


G-8 


1,052 


Piatt 


Erie 


D-3 


1,180 


Whiteside 


Champaign 


H-7 


39,563 


Champaign 


Eureka* 


E.6 


2,367 


Woodford 


Charleston * 


H-9 


9,164 


Coles 


Evanston 


J-2 


73,641 


Cook 


Chatsworth 


G-6 


1,119 


Livingston 


Evergreen Park 


J-3 


10,531 


Cook 


Chenoa 


G-6 


1,452 


McLean 


Fairbury 


G-6 


2,433 


Livingston 


Chester * 


D-14 


5,389 


Randolph 


Fairfield* 


G-12 


5,576 


Wayne 


Chicago* 


J-2 


3,620,962 


Cook 


Fairmont City 


D-12 


2,284 


St. Clair 


Chicago Hts. 


J-3 


24,551 


Cook 


Farmer City 


G-7 


1,752 


De Witt 


ChUlicothe 


E-5 


2,767 


Peoria 


Farmington 


D.6 


2,651 


Fulton 


Chrisman 


J-8 


1,071 


Edgar 


Flora 


G-12 


5,255 


Clay 


Christopher 


F-14 


3,545 


Franklin 


Flossmoor 


J-3 


1,804 


Cook 


Cicero 


J-2 


67,544 


Cook 


Forest Park 


J-2 


14,969 


Cook 


Clarendon HUls 


H-3 


2,437 


Du Page 


Forrest 


G-5 


1,040 


Livingston 


Clay City 


G-11 


1,103 


Clay 


Forreston 


E-2 


1,048 


Ogle 


Clinton * 


F-7 


5,945 


De Witt 


Fox Lake 


H-1 


2,238 


Lake 


Coal City 


G-4 


2,220 


Grundy 


Fox River Grove 


H-1 


3,313 


McHenry 


Cobden 


E-1 5 


1,104 


Union 


Franklin Park 


H-2 


8,899 


Cook 


Colchester 


B-7 


1,551 


McDonough 


Frecburg 


D-12 


1,661 


St. Clair 


Collinsville 


D-12 


11,862 


Madison- 


Freeport * 


E-1 


22,467 


Stephenson 








St. Clair 


Fulton 


D-2 


2,706 


Whiteside 


Columbia 


C-12 


2,179 


Monroe 


Galena * 


C-1 


4,648 


Jo Daviess 


Coulterville 


E-13 


1,160 


Randolph 


Galesburg* 


C-5 


31,425 


Knox 


Crete 


J-3 


2,298 


Will 


Galva 


D-4 


2,886 


Henry 


Creve Coeur 


E-6 


5,499 


Tazewell 


Gcneseo 


D-3 


4,325 


Henry 


Crotty 


G-4 


1,435 


La Salle 


Geneva* 


G-2 


5.139 


Kane 


Crystal Lake 


G-1 


4,832 


McHcnry 


Genoa 


G-2 


1,690 


DcKalb 


Cuba 


C-6 


1,482 


Fulton 


Georgetown 


J-8 


3,294 


Vermilion 








• Count) 


• Seat 






55 



Place 


Map 
Coordinate 


Population 


County 


Place 


Map 
Coordinate 


Population 


County 


Gibson 


G-6 


3,029 


Ford 


LawrenccviUe * 


J-Il 


6,328 


LaviTence 


Gillespie 


D-10 


4,105 


Macoupin 


Lebanon 


D-12 


2,417 


St. Clair 


Gilman 


H-5 


1,602 


Iroquois 


Lemont 


H-3 


2,757 


Cook 


Girard 


D-9 


1,740 


Macoupin 


Lena 


D-1 


1,227 


Stephenson 


Glen Carbon 


D-11 


1,176 


Madison 


Le Roy 


F-7 


1,820 


McLean 


Glencoe 


J-1 


6,980 


Cook 


Lcwistown * 


D-7 


2,630 


Fulton 


Glen EUyn 


H-2 


9,524 


Du Page 


Lexington 


F-6 


1,181 


McLean 


Glenview 


J-2 


6,142 


Cook 


Libertyville 


H-1 


5,425 


Lake 


Golconda * 


G-15 


1,066 


Pope 


Lincoln * 


E-7 


14,362 


Logan 


Grafton 


C-11 


1,117 


Jersey 


Lincolnwood 


J-2 


3,072 


Cook 


Grandview 


E-8 


1,349 


Sangamon 


Litchfield 


E-1 


7,208 


Montgomery 


Granite City 


C-12 


29,465 


Madison 


Lockport 


H-3 


4,955 


Will 


Grays Lake 


H-1 


1,970 


Lake 


Lombard 


H-2 


9,817 


Du Page 


Grayville 


H-13 


2,461 


White- 


Loves Park 


F-1 


5,366 


Winnebago 








Edwards 


Lovington 


G-9 


1,152 


Moultrie 


Greenup 


H-10 


1,360 


Cumberland 


Lyons 


J-2 


6,120 


Cook 


Greenville* 


E-11 


4,069 


Bond 


McHenry 


H-1 


2,080 


McHenry 


Griggs ville 


B-9 


1,199 


Pike 


McLeansboro * 


G-1 3 


3,008 


Hamilton 


Gurnee 


H-1 


1,097 


Lake 


Mackinaw 


E-6 


1,011 


Tazewell 


Hamilton 


A-7 


1,776 


Hancock 


Macomb* 


B-6 


10,592 


McDonough 


Hanover 


C-1 


1,643 


Jo Daviess 


Madison 


C-12 


7,963 


Madison 


Harrisburg* 


G-14 


10,999 


Saline 


Mahomet 


G-7 


1,017 


Champaign 


Hartford 


D-U 


1,909 


Madison 


Manteno 


J-4 


1,789 


Kankakee 


Harvard 


G-1 


3,464 


McHenry 


Marengo 


G-1 


2,726 


McHenry 


Harvey 


J-3 


20,683 


Cook 


Marion* 


F-14 


10,459 


Williamson 


Havana * 


D-7 


4,398 


Mason 


Marissa 


D-1 3 


1,652 


St. Clair 


Hazel Crest 


J-3 


2,129 


Cook 


Markham 


J-3 


2,753 


Cook 


Henry 


E-5 


1,966 


Marshall 


Maroa 


F-8 


1,100 


Macon 


Herrin 


F-14 


9,331 


Williamson 


Marseilles 


G-4 


4,514 


La Salle 


Heyworth 


F-7 


1,072 


McLean 


Marshall * 


J-9 


2,960 


Clark 


Highland 


D-11 


4,283 


Madison 


Martinsville 


H-10 


1,440 


Clark 


Highland Park 


J-1 


16,808 


Lake 


Mascoutah 


D-12 


3,009 


St. Clair 


Highwood 


J-1 


3,813 


Lake 


Mason City 


D-7 


2,004 


Mason 


Hillsboro* 


E-10 


4,141 


Montgomery 


Matteson 


J-3 


1,211 


Cook 


Hillside 


H-2 


2,131 


Cook 


Mattoon 


G-9 


17,547 


Coles 


Hinsdale 


H-3 


8,676 


Du Page- 


Maywood 


J-2 


27,473 


Cook 








Cook 


Melrose Park 


J-2 


13,366 


Cook 


Homer 


H-8 


1,030 


Champaign 


Mendota 


F-3 


5,129 


La Salle 


Homewood 


J-3 


5,887 


Cook 


Merrionette Park 


J-3 


1,101 


Cook 


Hoopeston 


J-6 


5,992 


Vermilion 


Metamora 


E-5 


1,368 


Woodford 


Itasca 


H-2 


1,274 


Du Page 


Metropolis * 


G-1 6 


6,093 


Massac 


Jacksonville * 


C-9 


20,387 


Morgan 


Midlothian 


J-3 


3,216 


Cook 


Jerseyville* 


C-10 


5,792 


Jersey 


Milan 


C-4 


1,737 


Rock Island 


Johnson City 


F-U 


4,479 


Williamson 


Milford 


J-6 


1,648 


Iroquois 


Joliet* 


H-3 


51,601 


Will 


MiUedgeville 


D-2 


1,044 


Carroll 


Jonesboro * 


E-15 


1,607 


Union 


Millstadt 


D-12 


1,566 


St. Clair 


Kankakee* 


H-4 


25,856 


Kankakee 


Minonk 


F-5 


1,955 


Woodford 


Keithsburg 


B-5 


1,006 


Mercer 


Moline 


C-3 


37,397 


Rock Island 


Kenilworth 


J-2 


2,789 


Cook 


Momence 


J-4 


2,644 


Kankakee 


Kewanee 


D-4 


16,821 


Henry 


Monmouth* 


C-5 


10,193 


Warren 


Kincaid 


E-9 


1,793 


Christian 


Monticello* 


G-8 


2,612 


Piatt 


Knoxville 


C-5 


2,209 


Knox 


Morris* 


G-4 


6,926 


Grundy 


Lacon * 


E-5 


2,020 


Marshall 


Morrison * 


D-3 


3,531 


Whiteside 


Ladd 


F-3 


1,224 


Bureau 


Morrisonville . 


E-9 


1,182 


Christian 


La Grange 


H-2 


12,002 


Cook 


Morton 


E-6 


3,692 


Tazewell 


La Grange Park 


H-2 


6,176 


Cook 


Morton Grove 


J-2 


3,926 


Cook 


La Harpe 


B-6 


1,295 


Hancock 


Mound City* 


F-1 6 


2,167 


Pulaski 


La Salle 


F-4 


12,083 


La Salle 


Mounds 


F-1 6 


2,001 


Pulaski 


Lake Bluff 


J-1 


2,000 


Lake 


Mount Carmel * 


J-12 


8,732 


Wabash 


Lake Forest 


J-1 


7,819 


Lake 


Mount Carroll * 


D-2 


1,950 


Carroll 


Lanark 


D-2 


1,359 


Carroll 


Mount Morris 


E-2 


2,709 


Ogle 


Lansing 


J-3 


8,682 


Cook 


Mount Olive 


D-10 


2,401 


Macoupin 


56 






*Cour 


ity Seat 









Place 


Map 

Coordmatf 


Population 


County 


Coordinate 


Population 


Counl\ 


Mount Prosprct 


H-2 


4,009 


c:ook 


Port Byron 


C-3 


1,050 


Rock Island 


Mount Pulaski 


i:-8 


1,526 


Logan 


Posen 


J-3 


1,795 


Cook 


Mount Sterling * 


B.8 


2,246 


Brown 


Princeton * 


E-4 


5,765 


Bureau 


Mount Vernon * 


F-13 


15,600 


JefTerson 


Princeville 


D-5 


1,113 


Peoria 


Moweaqua 


F-9 


1,475 


Shelby 


Prophctstown 


D-3 


1,691 


Whiteside 


Mundclein 


H-1 


3,189 


Lake 


Quincy * 


A-8 


41,450 


Adams 


Murphysboro * 


F,-14 


9,241 


Jackson 


Rantoul 


H-7 


6,387 


Champaign 


Naperville 


H-3 


7,013 


Du Page 


Red Bud 


D-13 


1,519 


Randolph 


Nashville* 


E-13 


2,432 


Washington 


Ridgway 


H-14 


1,148 


Gallatin 


Nauvoo 


A-6 


1,242 


Hancock 


Riverdale 


J-3 


5,840 


Cook 


Neoga 


G-10 


1,125 


Cumberland 


River Forest 


J-2 


10,823 


Cook 


New Athens 


D-13 


1,518 


St. Clair 


River Grove 


J-2 


4,839 


Cook 


New Baden 


D-12 


1,428 


Clinton- 


Riverside 


H-2 


9,153 


Cook 








St. Clair 


River ton 


E-8 


1,450 


Sangamon 


New Lenox 


H-3 


1,235 


Will 


Roanoke 


F-5 


1,368 


Woodford 


Newman 


H-8 


1,140 


Douglas 


Robbins 


J-3 


4,766 


Cook 


Newton* 


H-11 


2,780 


Jasper 


Robinson * 


J-11 


6,407 


Crawford 


Niles 


J-2 


3,587 


Cook 


Rochelle 


F-2 


5,449 


Ogle 


Nokomis 


E-10 


2,544 


Montgomery 


Rockdale 


H-3 


1,393 


Will 


Normal 


F-6 


9,772 


McLean 


Rock Falls 


D-3 


7,983 


Whiteside 


Norridge 


J-2 


3,428 


Cook 


Rockford * 


F-1 


92,927 


Winnebago 


Norris City 


G-14 


1,370 


White 


Rock Island * 


C-3 


48,710 


Rock Island 


Northbrook 


J-1 


3,348 


Cook 


Rockton 


F-1 


1,432 


Winnebago 


North Chicago 


J-1 


8,628 


Lake 


Roodhouse 


C-9 


2,368 


Greene 


North Chillicothc 


E-S 


1,741 


Peoria 


Roselle 


H-2 


1,038 


Du Page 


Northfield 


J-2 


1,426 


Cook 


Roseville 


B.6 


1,080 


Warren 


North Lake 


H-2 


4,361 


Cook 


Rosiclarc 


G-15 


2,086 


Hardin 


North Pekin 


E-6 


1,758 


Tazewell 


Rossvillc 


J-7 


1,382 


Vermilion 


North Riverside 


J-2 


3,230 


Cook 


Round Lake Beach 


H-1 


1,892 


Lake 


Oak Forest 


J-3 


1,856 


Cook 


Round Lake Park 


H-1 


1,836 


Lake 


Oak Lawn 


J-3 


8,751 


Cook 


Roxana 


D-U 


1,911 


Madison 


Oak Park 


J-2 


63,529 


Cook 


Royal ton 


F-14 


1,506 


Franklin 


Oblong 


H-11 


1,639 


Crawford 


Rushville * 


C-7 


2,682 


Schuyler 


Odin 


F-12 


1,341 


Marion 


St. Anne 


J-5 


1,403 


Kankakee 


O'Fallon 


D.12 


3,022 


St. Clair 


St. Charles 


G-2 


6,709 


Kane 


Oglesby 


F-4 


3,922 


La Salle 


St. Elmo 


F-11 


1,716 


Fayette 


Olney* 


H-11 


8,612 


Richland 


St. FrancisviUc 


J-12 


1,117 


Lawrence 


Onarga 


H-6 


1,455 


Iroquois 


Salem* 


F-12 


6,159 


Marion 


Oregon • 


E-2 


3,205 


Ogle 


Sandoval 


F-12 


1,531 


Marion 


Oswego 


G-3 


1,220 


Kendall 


Sandwich 


G-3 


3,027 


DcKalb 


Ottawa • 


F-4 


16,957 


La Salle 


Savanna 


D-2 


5,058 


Carroll 


Palatine 


H-2 


4,079 


Cook 


Schiller Park 


H-2 


1,384 


Cook 


Palestine 


J-11 


1,589 


Crawford 


Sesser 


F-13 


2,086 


Franklin 


Pana 


F-9 


6,178 


Christian 


Shawnectown * 


H-14 


1,917 


Gallatin 


Paris* 


J-9 


9,460 


Edgar 


Shelbyville* 


F-9 


4,462 


Shelby 


Park Forest 


J-3 


8,130 


Cook 


Sheldon 


J-5 


1,114 


Iroquois 


Park Ridge 


H-2 


16,602 


Cook 


Silvis 


C-3 


3,055 


Rock Island 


Paxton • 


H-6 


3,795 


Ford 


Skokic 


J-2 


14,832 


Cook 


Pccatonica 


E-1 


1,438 


Winnebago 


South Bcloit 


F-1 


3,221 


Winnebago 


Pekin * 


E-6 


21,858 


Tazewell 


South Chicago Hts. 


J-3 


2,129 


Cook 


Peoria* 


E-6 


111,856 


Peoria 


South Elgin 


G-2 


1,220 


Kane 


Peoria Heights 


E-6 


5,425 


Peoria 


South Holland 


J-3 


3,247 


Cook 


Peotone 


J-4 


1,395 


Will 


South Jacksonville 


C-9 


1,165 


Morgan 


Peru 


F-4 


8,653 


La Salle 


South Pekin 


E.6 


1,043 


Tazewell 


Petersburg * 


D-8 


2,325 


Menard 


Sparta 


D.13 


3,576 


Randolph 


Phoenix 


J-3 


3,606 


Cook 


Springfield * 


E-8 


81,628 


Sangamon 


Pinckneyville * 


E-13 


3,299 


Perry 


Spring X'allcy 


F-4 


4.916 


Bureau 


Pittsfield* 


B.9 


3,564 


Pike 


Staunton 


D-11 


4,047 


Macoupin 


Plainfield 


H-3 


1,764 


Will 


Steel ville 


i:-14 


1,353 


Randolph 


Piano 


G-3 


2,154 


Kendall 


Stcgcr 


J-3 


4,358 


Will-Cook 


Polo 


E-2 


2,242 


Ogle 


Sterling 


D-3 


12,817 


Whiteside 


Pontiac * 


G-5 


8,990 


Livingston 


Stickney 


J-2 


3,317 


Cook 








• Count 


y Scat 






^7 



Place 


Map 
Coordinate 


Population 


County 


Place 


Map 
Coordinate 


Population 


County 


Stockton 


D-1 


1,445 


Jo Daviess 


Wauconda 


H-1 


1,173 


Lake 


Stone Park 


J-2 


1,414 


Cook 


Waukegan * 


J-1 


38,946 


Lake 


Stonington 


F-9 


1,120 


Christian 


Wavcrly 


D-9 


1,330 


Morgan 


Streator 


F-4 


16,469 


La Salle- 


Wenona 


F-5 


1,005 


Marshall 








Livingston 


Westchester 


H-2 


4,308 


Cook 


Sullivan * 


G-9 


3,470 


Moultrie 


West Chicago 


H-2 


3,973 


Du Page 


Summit 


J-3 


8,957 


Cook 


West City 


F-14 


1,081 


Franklin 


Sumner 


J-11 


1,170 


Lawrence 


West Dundee 


H-2 


1,948 


Kane 


Swansea 


D-1 2 


1,816 


St. Clair 


Western Springs 


H-2 


6,364 


Cook 


Sycamore * 


G-2 


5,912 


De Kalb 


West Frankfort 


F-14 


11,384 


Franklin 


Taylorville * 


E-9 


9,188 


Christian 


Westmont 


H-3 


3,402 


Du Page 


Thornton 


J-3 


1,217 


Cook 


Westville 


J-8 


3,196 


Vermilion 


Tilton 


J-7 


1,638 


Vermilion 


Wheaton * 


H-2 


11,638 


Du Page 


Tinley Park 


J-3 


2,326 


Cook 


White Hall 


C-9 


3,082 


Greene 


Tolono 


H-8 


1,065 


Champaign 


Willow Springs 


H-3 


1,314 


Cook 


Toluca 


F-5 


1,419 


Marshall 


Wilmette 


J-2 


18,162 


Cook 


Toulon * 


D-5 


1,173 


Stark 


Wilmington 


H-4 


3,354 


Will 


Tremont 


E-6 


1,138 


Tazewell 


Winchester* 


C-9 


1,591 


Scott 


Trenton 


E-12 


1,432 


Clinton 


Windsor 


G-9 


1,008 


Shelby 


Troy 


D-11 


1,260 


Madison 


Winnetka 


J-2 


12,105 


Cook 


Tuscola * 


H-8 


2,960 


Douglas 


Winthrop Harbor 


J-2 


1,765 


Lake 


Urbana* 


H-7 


22,834 


Champaign 


Witt 


E-10 


1,156 


Montgomery 


Vandalia * 


F-11 


5,471 


Fayette 


Wood Dale 


H-2 


1,857 


Du Page 


Venice 


C-12 


6,226 


Madison 


Wood River 


D-11 


10,190 


Madison 


Vienna* 


F-15 


1,085 


Johnson 


Woodstock * 


G-1 


7,192 


McHenry 


Villa Grove 


H-8 


2,026 


Douglas 


Worth 


J-3 


1,472 


Cook 


Villa Park 


H-2 


8,821 


Du Page 


Wyoming 


D-5 


1,496 


Stark 


Virden 


D-9 


3,206 


Macoupin 


Zeigler 


F-14 


2,516 


Franklin 


Virginia* 


C-8 


1,572 


Cass 


Zion 


J-1 


8,950 


Lake 


Walnut 


E-3 


1,093 


Bureau- 
















Washington 


County Seats WITH 


Populations OF Less TH 


ANl000iNl950 


Wamac 


F-12 


1,429 


Marion- 
















Clinton 


Elizabethtown * 


G-1 5 


583 


Hardin 


Warren 


D-1 


1,378 


Jo Daviess 


Hardin * 


C-10 


928 


Calhoun 


Warsaw 


A-7 


2,002 


Hancock 


Hennepin * 


E-4 


312 


Putnam 


Washington 


E-6 


4,285 


Tazewell 


Louisville* 


G-11 


970 


Clay 


Washington Park 


D-1 2 


5,840 


St. Clair 


Oquawka * 


B-5 


929 


Henderson 


Waterloo* 


C-13 


2,821 


Monroe 


Toledo* 


H-10 


905 


Cumberland 


Watseka* 


J-5 


4,235 


Iroquois 


Yorkville* 


G-3 


632 


Kendall 



' County Seat 



58 



LAKE. COOK. 
AND DU PAGE 
COUNTIES 



® EVANSTON 



w Ch Elmhurstg ' " g.' K. ^ 




'J 



Park Forest • S. ChicaBO His. 



MADISON AND 
SAINT CLAIR 
COUNTIES 



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URBAN POPULATION ^.h" °' 

AND LOCATION "-^, 

Incorporated Cities and ™' mo,™. 

Towns with Populations | * 

of 1,000 or More p„, J„'; 

U. S. Census, 1950 „. E. Molins 

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