Illinoisis in themidwestern United States.SurroundingstatesareWisconsinto the north,IowaandMissourito the west,Kentuckyto the east and south, andIndianato the east. Illinois also bordersMichigan,but only via a northeastern water boundary inLake Michigan.Nearly the entire western boundary of Illinois is theMississippi River,except for a few areas where the river has changed course. Illinois' southeastern and southern boundary is along theWabash Riverand theOhio River,whereas its northern boundary and much of its eastern boundary are straight survey (longitudinal and latitudinal) lines. Illinois has a maximum north–south distance of 390 miles (630 km) and 210 miles (340 km) east-west. Its total area is 57,918 square miles (150,010 km2).
Statistics
edit- Illinois has a maximum north–south distance of 390 miles (630 km) and 210 miles (340 km) east-west.
- Total area is 57,918 square miles (150,010 km2), ranked 25th in size of the 50 states.
- Water area is 2,325 square miles (6,020 km2);Lake Michiganaccounts for most of this.
- Charles Moundin the northwestDriftless Areais the highest point in the state at 1,235 feet (376 m) above sea level.
- TheMississippi RiveratCairo, Illinoisis the lowest point, at 279 feet (85 m).
- Average elevation is 600 feet (180 m) above sea level.
- McLean Countyis the largest county in terms of land area (1,184 sq mi.), whileCook Countyis the largest county in terms of population (5,275,541 as of 2020), and the largest when land and water area are combined.[1]
Geographical divisions
editIllinois has three major geographical divisions: Northern, Central, and Southern. Collectively, central and southern Illinois are often referred to within Illinois as "downstate Illinois"but with political developments since World War II" Downstate "now generally refers toallof Illinois outside of the Chicago metro area.
Northern Illinois
editNorthern Illinoisis dominated by theChicago metropolitan area,including the city ofChicago,its suburbs, and the adjoining exurban area into which the metropolis is expanding. The "collar counties"are the five counties that surround the centrally located Cook County in the Chicago metropolitan area: DuPage County, Kane County, Lake County, McHenry County, and Will County.[2]The term "Chicagoland"is sometimes used to describe the metro area, including Chicago, its suburbs within Cook County, and the so-called collar counties. The term is said to have been coined byChicago TribunepublisherRobert R. McCormick.[2]TheChicagoland Chamber of Commercedefines it as all of Cook, and DuPage, Kane, Lake, McHenry and Will counties.[3]The region is cosmopolitan, densely populated, industrialized, and settled by a wide variety of ethnic groups. As defined by the federal government, the Chicago Metropolitan Area includes two counties in Indiana, two counties in Wisconsin, and the following 11 counties in Illinois:Cook,DeKalb,DuPage,Grundy,Kane,Kankakee,Kendall,Lake,LaSalle,McHenry,andWillcounties.
TheRockford Metropolitan Areais north-central nearWisconsin,on theRock River.TheQuad Cities Metropolitan Areais on both sides of theMississippi Riverseparating Illinois fromIowa.The Illinois side includesHenry County,Mercer County,andRock Island County.[4]
In extreme northwestern Illinois theDriftless Zone,a region of unglaciated and therefore higher and morerugged topography,occupies a small part of the state.Charles Mound,located in this region, is the state's highest elevation abovesea level.
Central Illinois
editSouthward and westward, the second major division isCentral Illinois,an area of mostly flatprairiewith the exception of areas along the Illinois and Mississippi rivers that are steeped in hills and bluffs hanging high above the rivers providing commanding views for miles. The western section (west of the Illinois River) was originally part of theMilitary Tract of 1812and forms the distinctive western bulge of the state. Central Illinois is characterized by small towns and mid-sized cities. Agriculture, particularlycornandsoybeans,figures prominently. Major cities includePeoria,andSpringfield(the state capital). TheChampaign-Urbana Metropolitan Areais located in the central region of the state and is composed ofChampaign,Ford,andPiattcounties.[5]
Southern Illinois
editThe third division isSouthern Illinois,comprising the area south ofU.S. Route 50,and includingLittle Egypt,near the juncture of theMississippi RiverandOhio River.This region can be distinguished from the other two by its warmer climate, different mix of crops (includingcottonfarming in the past), more rugged unglaciated topography, as well as small-scale oil deposits andcoalmining.
The population in southern Illinois is concentrated in two areas:
- Metro-Eastis an area east ofSt. Louisand it includesJersey,Madison,St. Clair,Macoupin,and parts ofBondandCalhounfrom theSt. Louis Metropolitan Statistical Area,as well asClinton County.[6]
- Carbondale,Marion, West Frankfort, Benton, Herrin, Murphysboro, Carterville, and the Johnston City area.
TheShawnee Hillsarise in southern Illinois.Illinoian Stage,about 132,000 to 300,000 years before present, climbed the northern face of the Shawnee Hills, but did not reach the summit. Most of the Shawnee Hills is therefore unglaciated.
The floodplain on the Mississippi River fromAltonto theKaskaskia Riveris theAmerican Bottom,and is the site of the ancient city ofCahokia,and was a region of early French settlement, as well as the site of the first state capital, atKaskaskia.The extreme southern tip of Illinois is in theGulf Coastal Plain.
Political geography
editThe city of Chicago and some of its older suburbs are heavilyDemocratic.While this tendency has historically been balanced byRepublicanvoters in the suburbs, Democrats have significantly increased their suburban support in the past decade. Central Illinois's largely rural character helps to sustain a largely Republican voting pattern and widespread antipathy toward Chicago. The combination of poorer soil, coal mining and industrialization has caused the southern region to lean Democratic politically, especially in the urbanized region aroundSaint Louis,Missouri.
Rockford, Illinoisis known as a center of liberal"gypsy moth" Republicans.
Geology
editIllinois is predominantly covered with soil, hundreds of feet thick in many places. Much of this soil is called, appropriately, "Illite",and is the most common type of soil on the planet. The visible geology of the state is mainlyQuaternary,with rocks buried deeply. The wealth of the state mainly arises from this abundance of soil and the favorable agrarian conditions it provides.
Illinois is a majorcoal-producing state. Much of the bedrock surface is ofPennsylvanianage, including "cyclothemes", regular sequences of limestone, shale and coal layers. Newer rocks may have once existed in the State, but these have been removed by repeated epochs of glaciation. Only tiny areas of newer bedrock exist. The chance of finding dinosaur bones in Illinois is almost nil:[citation needed],the Pennsylvanian rocks were here before the dinosaurs.
Galena,aleadore, has been mined in the northwest corner of the state. The ore was processed aroundPeru, Illinois,where river transport was available to bring the ore to a source of coal. About six tons of coal are needed for each ton of ore.
Fluorite,calcium fluoride,is the state mineral. It is mined in the southeastern portion of the state, aroundMetropolis.Fluorine gas is produced from fluorite. This is used in the production ofuranium hexafluoridein Metropolis, Illinois for use at thegaseous diffusionplant inPaducah, Kentucky.
Geodescan be found in the olderMississippianoutcroppings along theMississippi River.
Igneousintrusions are found in the far southern areas of the State. Ages ago North America began to split roughly along the lines of the Ohio and Mississippi Rivers. Igneous rock flowed up into fissures, as a new ocean began to form. Had this continued, Illinois might have resembled theArabian Peninsula,a broken terrain between two continents. This split, however, failed: the continent reclosed, leaving only a few igneous intrusions, and some oil fields, as evidence that it happened.
North of theIllinois Riverthe bedrock surface is much olderOrdoviciansandstone. This sandstone yields ancient sand that is very useful in the production of glass, and in making molds for metal castings.
Coal
editThe majority of Illinois surfacebedrockbelongs to thePennsylvanianperiod, particularly the downstate region. About 68% of the state hascoal-bearing strata of this geologic period. According to theIllinois State Geological Survey,211 billion tons ofbituminous coalare estimated to lie under the surface, having a total heating value greater than the estimated oil deposits in theArabian Peninsula.However, this coal has a highsulfurcontent and as such requires special equipment to reduce air pollution.
Rivers
editIllinois is mainly bounded by rivers, and theIllinois Riverbisects the state. A few rivers, including theFoxandRockRivers enter the State from Wisconsin. TheIroquoisandKankakeearise inIndiana,but lose their identity before reaching theMississippi.The North Fork of the Vermilion River arises in Indiana, but joins theVermilion,which exits the state before joining theWabash Riverin Indiana. Other rivers include theOhio River,theKaskaskia River,theSangamon Riverand theChicago River.TheCashe Riverarea in southern Illinois forms the basis for aRamsar ConventionWetland of International Importance.
Groundwater
editSubsurface water is generally plentiful in Illinois. However, irregular gravel deposits from glaciation can lead to difficulties predicting depth of the water table.
TheMahomet Aquiferis a large aquifer used as a source for public water supply by many communities in Central Illinois.
Flora and fauna
editLargemammalspecies currently found in Illinois includewhitetail deerandcoyote,with the latter becoming urbanized in theChicagoarea, as well as common in the rural areas. Furbearers commonly found includeopossum,raccoon,mink,redandgray foxes,andmuskrat.Commonly seen lagomorphs include thecottontail rabbitand commonly seen rodents includesquirrels.Game birds found includeCanada goose,mallard duck,ruffed grouse,wild turkey,andbobwhite quail.Thenorthern cardinalis the official state bird. The state has approximately 300 species of birds, many of which migrate on theMississippi Flyway.Extensive wetland restoration along theMississippi RiverandIllinois Riverare attracting many species.
About two thirds of the state was originally prairie, with much of the area converted to rowcrop farming, while the southern third of the state remains heavily forested withoak,hickory,andmaple.Also, several prairie plants.
Especially in the northern third of the state,intensive agriculturehas made some species rare, while population numbers are increasing in the less-developed south. Large mammals generallyno longer foundin the wild in Illinois includeAmerican bison,gray wolf,American black bear,andelk.
Climate
edit
Illinois has acontinental climate,with large temperature extremes not moderated by either mountains or oceans. Weather is influenced primarily by cold Canadian Arctic air in the winter, and warm, humid air from theGulf of Mexicoin the summer. High temperatures in the south of the state are about 10 to 12 °F. warmer than the north. Average annual temperature is 47 °F. in the north and 58 °F. in the south. Temperatures greater than 90 °F. occur about 45 days per year in the south, and 12 days per year in the north. Temperatures below zero °F. occur one day or less per year in the south, and 12 days per year in the north. Annual rainfall is 34 inches (860 mm) in the north and 46 inches (1,200 mm) in the south.
Prevailingwindsare from the west. Average wind speeds "blowing off theprairie"are greater in theChicagoarea. Statewide, the wind speeds average 8 to 12 miles per hour (13 to 19 km/h), and is greater in the winter than in summer.
Snowfall averages 30 inches (760 mm) in the north and 10 inches (250 mm) in the south, although the actual snowfalls vary greatly by year. In some years, southern Illinois receives very little snowfall, and may never get typical winter weather.
Most of the state has four distinct seasons. The southernmost part of the state is heavily forested and the trees are noted for having beautifulfallcolors.
Tornadoesare a common hazard, primarily in the central part of the state, with peak months in June and April. Freezing rain is most common in central Illinois.
| Climate data for Chicago (Midway International Airport), 1991–2020 normals,[a]extremes 1928–present | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Month | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Year |
| Record high °F (°C) | 67 (19) |
75 (24) |
86 (30) |
92 (33) |
102 (39) |
107 (42) |
109 (43) |
104 (40) |
102 (39) |
94 (34) |
81 (27) |
72 (22) |
109 (43) |
| Mean maximum °F (°C) | 53.4 (11.9) |
57.9 (14.4) |
72.0 (22.2) |
81.5 (27.5) |
89.2 (31.8) |
93.9 (34.4) |
96.0 (35.6) |
94.2 (34.6) |
90.8 (32.7) |
82.8 (28.2) |
68.0 (20.0) |
57.5 (14.2) |
97.1 (36.2) |
| Mean daily maximum °F (°C) | 32.8 (0.4) |
36.8 (2.7) |
47.9 (8.8) |
60.0 (15.6) |
71.5 (21.9) |
81.2 (27.3) |
85.2 (29.6) |
83.1 (28.4) |
76.5 (24.7) |
63.7 (17.6) |
49.6 (9.8) |
37.7 (3.2) |
60.5 (15.8) |
| Daily mean °F (°C) | 26.2 (−3.2) |
29.9 (−1.2) |
39.9 (4.4) |
50.9 (10.5) |
61.9 (16.6) |
71.9 (22.2) |
76.7 (24.8) |
75.0 (23.9) |
67.8 (19.9) |
55.3 (12.9) |
42.4 (5.8) |
31.5 (−0.3) |
52.4 (11.3) |
| Mean daily minimum °F (°C) | 19.5 (−6.9) |
22.9 (−5.1) |
32.0 (0.0) |
41.7 (5.4) |
52.4 (11.3) |
62.7 (17.1) |
68.1 (20.1) |
66.9 (19.4) |
59.2 (15.1) |
46.8 (8.2) |
35.2 (1.8) |
25.3 (−3.7) |
44.4 (6.9) |
| Mean minimum °F (°C) | −3 (−19) |
3.4 (−15.9) |
14.1 (−9.9) |
28.2 (−2.1) |
39.1 (3.9) |
49.3 (9.6) |
58.6 (14.8) |
57.6 (14.2) |
45.0 (7.2) |
31.8 (−0.1) |
19.7 (−6.8) |
5.3 (−14.8) |
−6.5 (−21.4) |
| Record low °F (°C) | −25 (−32) |
−20 (−29) |
−7 (−22) |
10 (−12) |
28 (−2) |
35 (2) |
46 (8) |
43 (6) |
29 (−2) |
20 (−7) |
−3 (−19) |
−20 (−29) |
−25 (−32) |
| Averageprecipitationinches (mm) | 2.30 (58) |
2.12 (54) |
2.66 (68) |
4.15 (105) |
4.75 (121) |
4.53 (115) |
4.02 (102) |
4.10 (104) |
3.33 (85) |
3.86 (98) |
2.73 (69) |
2.33 (59) |
40.88 (1,038) |
| Average snowfall inches (cm) | 12.5 (32) |
10.1 (26) |
5.7 (14) |
1.0 (2.5) |
0.0 (0.0) |
0.0 (0.0) |
0.0 (0.0) |
0.0 (0.0) |
0.0 (0.0) |
0.1 (0.25) |
1.5 (3.8) |
7.9 (20) |
38.8 (99) |
| Average precipitation days(≥ 0.01 in) | 11.5 | 9.4 | 11.1 | 12.0 | 12.4 | 11.1 | 10.0 | 9.3 | 8.4 | 10.8 | 10.2 | 10.8 | 127.0 |
| Average snowy days(≥ 0.1 in) | 8.9 | 6.4 | 3.9 | 0.9 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.2 | 1.6 | 6.3 | 28.2 |
| Averageultraviolet index | 1 | 2 | 4 | 6 | 7 | 9 | 9 | 8 | 6 | 4 | 2 | 1 | 5 |
| Source 1:NOAA[7][8][9],WRCC[10] | |||||||||||||
| Source 2: Weather Atlas (UV)[11] | |||||||||||||
| Climate data for Chicago (O'Hare Int'l Airport), 1991–2020 normals,[a]extremes 1871–present[b] | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Month | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Year |
| Record high °F (°C) | 67 (19) |
75 (24) |
88 (31) |
91 (33) |
98 (37) |
104 (40) |
105 (41) |
102 (39) |
101 (38) |
94 (34) |
81 (27) |
71 (22) |
105 (41) |
| Mean maximum °F (°C) | 52.3 (11.3) |
56.8 (13.8) |
71.0 (21.7) |
80.9 (27.2) |
88.0 (31.1) |
93.1 (33.9) |
94.9 (34.9) |
93.2 (34.0) |
89.7 (32.1) |
81.7 (27.6) |
67.0 (19.4) |
56.4 (13.6) |
96.0 (35.6) |
| Mean daily maximum °F (°C) | 31.6 (−0.2) |
35.7 (2.1) |
47.0 (8.3) |
59.0 (15.0) |
70.5 (21.4) |
80.4 (26.9) |
84.5 (29.2) |
82.5 (28.1) |
75.5 (24.2) |
62.7 (17.1) |
48.4 (9.1) |
36.6 (2.6) |
59.5 (15.3) |
| Daily mean °F (°C) | 25.2 (−3.8) |
28.8 (−1.8) |
39.0 (3.9) |
49.7 (9.8) |
60.6 (15.9) |
70.6 (21.4) |
75.4 (24.1) |
73.8 (23.2) |
66.3 (19.1) |
54.0 (12.2) |
41.3 (5.2) |
30.5 (−0.8) |
51.3 (10.7) |
| Mean daily minimum °F (°C) | 18.8 (−7.3) |
21.8 (−5.7) |
31.0 (−0.6) |
40.3 (4.6) |
50.6 (10.3) |
60.8 (16.0) |
66.4 (19.1) |
65.1 (18.4) |
57.1 (13.9) |
45.4 (7.4) |
34.1 (1.2) |
24.4 (−4.2) |
43.0 (6.1) |
| Mean minimum °F (°C) | −4.5 (−20.3) |
0.5 (−17.5) |
11.8 (−11.2) |
25.6 (−3.6) |
36.7 (2.6) |
46.0 (7.8) |
54.5 (12.5) |
54.3 (12.4) |
41.8 (5.4) |
29.7 (−1.3) |
17.3 (−8.2) |
3.2 (−16.0) |
−8.5 (−22.5) |
| Record low °F (°C) | −27 (−33) |
−21 (−29) |
−12 (−24) |
7 (−14) |
27 (−3) |
35 (2) |
45 (7) |
42 (6) |
29 (−2) |
14 (−10) |
−2 (−19) |
−25 (−32) |
−27 (−33) |
| Averageprecipitationinches (mm) | 1.99 (51) |
1.97 (50) |
2.45 (62) |
3.75 (95) |
4.49 (114) |
4.10 (104) |
3.71 (94) |
4.25 (108) |
3.19 (81) |
3.43 (87) |
2.42 (61) |
2.11 (54) |
37.86 (962) |
| Average snowfall inches (cm) | 11.3 (29) |
10.7 (27) |
5.5 (14) |
1.3 (3.3) |
0.0 (0.0) |
0.0 (0.0) |
0.0 (0.0) |
0.0 (0.0) |
0.0 (0.0) |
0.2 (0.51) |
1.8 (4.6) |
7.6 (19) |
38.4 (98) |
| Average extreme snow depth inches (cm) | 6.3 (16) |
6.3 (16) |
4.0 (10) |
0.6 (1.5) |
0.0 (0.0) |
0.0 (0.0) |
0.0 (0.0) |
0.0 (0.0) |
0.0 (0.0) |
0.0 (0.0) |
1.5 (3.8) |
3.9 (9.9) |
9.8 (25) |
| Average precipitation days(≥ 0.01 in) | 11.0 | 9.4 | 10.8 | 12.3 | 12.5 | 11.1 | 9.7 | 9.4 | 8.5 | 10.5 | 10.0 | 10.6 | 125.8 |
| Average snowy days(≥ 0.1 in) | 8.5 | 6.4 | 4.0 | 1.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.2 | 1.6 | 6.1 | 27.8 |
| Averagerelative humidity(%) | 72.2 | 71.6 | 69.7 | 64.9 | 64.1 | 65.6 | 68.5 | 70.7 | 71.1 | 68.6 | 72.5 | 75.5 | 69.6 |
| Averagedew point°F (°C) | 13.6 (−10.2) |
17.6 (−8.0) |
27.1 (−2.7) |
35.8 (2.1) |
45.7 (7.6) |
55.8 (13.2) |
61.7 (16.5) |
61.0 (16.1) |
53.8 (12.1) |
41.7 (5.4) |
31.6 (−0.2) |
20.1 (−6.6) |
38.8 (3.8) |
| Mean monthlysunshine hours | 135.8 | 136.2 | 187.0 | 215.3 | 281.9 | 311.4 | 318.4 | 283.0 | 226.6 | 193.2 | 113.3 | 106.3 | 2,508.4 |
| Percentpossible sunshine | 46 | 46 | 51 | 54 | 62 | 68 | 69 | 66 | 60 | 56 | 38 | 37 | 56 |
| Source:NOAA(relative humidity, dew point and sun 1961–1990)[8][14][15] | |||||||||||||
Border anomalies
editTheMississippi Riveris the nominal western boundary of the state, except for locations where the river has changed course.Kaskaskia, Illinois,the first state capital, is now west of the river. The Mississippi, due to a flood, destroyed the old town of Kaskaskia, and occupies what was the lower channel of theKaskaskia River.A portion ofMissouriis east of the river, nearGrand Tower, Illinois.Similar "avulsions"are found along theOhio Riverborder withKentuckyand theWabash Riverborder withIndiana.
See also
editFootnotes
edit- ^abMean monthly maxima and minima (i.e. the expected highest and lowest temperature readings at any point during the year or given month) calculated based on data at said location from 1991 to 2020.
- ^Official records for Chicago were kept at various locations in downtown from January 1871 to December 31, 1925, University of Chicago from January 1, 1926 to June 30, 1942, Midway Airport from July 1, 1942 to January 16, 1980, and at O'Hare Airport since January 17, 1980.[12][13]
Notes
edit- ^"Decennial Census of Population and Housing".Census.gov.Retrieved2021-12-15.
- ^abFuller, Jack (2005)."Chicagoland".The Electronic Encyclopedia of Chicago.Chicago Historical Society.Archivedfrom the original on 6 April 2009.Retrieved20 February2010.
- ^Chicagoland Chamber of CommerceArchivedFebruary 9, 2009, at theWayback Machine
- ^"Welcome to the Quad Cities".City Guide Post Inc.Archivedfrom the original on 2008-01-16.Retrieved2008-02-02.
- ^Population in Metropolitan and Micropolitan Statistical Areas Ranked by 2000 Population for the United States and Puerto Rico: 1990 and 2000.Archived2018-07-18 at theWayback MachineU.S. Census Bureau. December 30, 2003. Accessed November 20, 2007,
- ^State of Illinois.Metro-East "Metro East: 1965 to Today", Illinois Labor Market ReviewArchived2011-03-02 at theWayback Machine
- ^ "Station: Chicago Midway AP 3SW, IL".U.S. Climate Normals 2020: U.S. Monthly Climate Normals (1991–2020).National Climatic Data Center.RetrievedMay 14,2021.
- ^ab "NowData – NOAA Online Weather Data".NWS Romeoville, IL.RetrievedMay 14,2021.
- ^ "Top 20 Weather Events of the Century for Chicago and Northeast Illinois 1900–1999".NWS Romeoville, IL.RetrievedJune 16,2014.
- ^ "Chicago Midway AP 3 SW, Illinois".Western Regional Climate Center.RetrievedJune 12,2014.
- ^ "Chicago, IL - Detailed climate information and monthly weather forecast".Weather Atlas.Yu Media Group.RetrievedJune 29,2019.
- ^"History of the Chicago and Rockford Weather Observation Sites".weather.gov.RetrievedNovember 9,2021.
- ^ThreadEx
- ^ "Station: Chicago Ohare Intl AP, IL".U.S. Climate Normals 2020: U.S. Monthly Climate Normals (1991–2020).National Oceanic and Atmospheric Administration.RetrievedMay 14,2021.
- ^ "Chicago/O'Hare, IL Climate Normals 1961–1990".National Oceanic and Atmospheric Administration.RetrievedJuly 18,2020.
References
edit- Harris, Stanley E.; C. W. Horrell; Daniel Irwin (1977).Exploring the Land and Rocks of Southern Illinois: A Geological Guide.Carbondale: Southern Illinois University Press.ISBN0809307405.
- Wiggers, Ray (1997).Geology Underfoot in Illinois.Missoula, Mont: Mountain Press Pub. Co.ISBN087842346X.