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List of Illinois Counties and County Seats





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The U.S. state of Illinois is divided into 102 counties. Explore list of California Counties and their County Seats in alphabetical order populations, areas and the date of formation.

List of Illinois Counties and County Seat

S.NCountyCounty SeatPopulation(2011)Area Formed
1Adams CountyQuincy67,103857 sq mi1825
2Alexander CountyCairo8,238236 sq mi1819
3Bond CountyGreenville17,768380 sq mi1817
4Boone CountyBelvidere54,165281 sq mi1837
5Brown CountyMount Sterling6,937306 sq mi1839
6Bureau CountyPrinceton34,978869 sq mi1837
7Calhoun CountyHardin5,089254 sq mi1825
8Carroll CountyMount Carroll15,387444 sq mi1839
9Cass CountyVirginia13,642376 sq mi1837
10Champaign CountyUrbana201,081997 sq mi1833
11Christian CountyTaylorville34,800709 sq mi1839
12Clark CountyMarshall16,335502 sq mi1819
13Clay CountyLouisville13,815469 sq mi1824
14Clinton CountyCarlyle37,762474 sq mi1824
15Coles CountyCharleston53,873508 sq mi1830
16Cook CountyChicago5,194,675946 sq mi1831
17Crawford CountyRobinson19,817444 sq mi1816
18Cumberland CountyToledo11,048346 sq mi1843
19DeKalb CountySycamore105,160634 sq mi1837
20DeWitt CountyClinton16,561398 sq mi1839
21Douglas CountyTuscola19,980417 sq mi1859
22DuPage CountyWheaton916,924334 sq mi1839
23Edgar CountyParis18,576624 sq mi1823
24Edwards CountyAlbion6,721222 sq mi1814
25Effingham CountyEffingham34,242479 sq mi1831
26Fayette CountyVandalia22,140716 sq mi1821
27Ford CountyPaxton14,081486 sq mi1859
28Franklin CountyBenton39,561412 sq mi1818
29Fulton CountyLewistown37,069866 sq mi1823
30Gallatin CountyShawneetown5,589324 sq mi1812
31Greene CountyCarrollton13,886543 sq mi1821
32Grundy CountyMorris50,063420 sq mi1841
33Hamilton CountyMcLeansboro8,457435 sq mi1821
34Hancock CountyCarthage19,104795 sq mi1825
35Hardin CountyElizabethtown4,320178 sq mi1839
36Henderson CountyOquawka7,331379 sq mi1841
37Henry CountyCambridge50,486823 sq mi1825
38Iroquois CountyWatseka29,7181,116 sq mi1833
39Jackson CountyMurphysboro60,218588 sq mi1816
40Jasper CountyNewton9,698494 sq mi1831
41Jefferson CountyMount Vernon38,827571 sq mi1819
42Jersey CountyJerseyville22,985369 sq mi1839
43Jo Daviess CountyGalena22,678601 sq mi1827
44Johnson CountyVienna12,582346 sq mi1812
45Kane CountyGeneva515,269521 sq mi1836
46Kankakee CountyKankakee113,449678 sq mi1853
47Kendall CountyYorkville114,736321 sq mi1841
48Knox CountyGalesburg52,919716 sq mi1825
49Lake CountyWaukegan703,462448 sq mi1839
50LaSalle CountyOttawa113,9241,135 sq mi1831
51Lawrence CountyLawrenceville16,833372 sq mi1821
52Lee CountyDixon36,031725 sq mi1839
53Livingston CountyPontiac38,9501,044 sq mi1837
54Logan CountyLincoln30,305618 sq mi1839
55Macon CountyDecatur110,768581 sq mi1829
56Macoupin CountyCarlinville47,765864 sq mi1829
57Madison CountyEdwardsville269,282725 sq mi1812
58Marion CountySalem39,437572 sq mi1823
59Marshall CountyLacon12,640386 sq mi1839
60Mason CountyHavana14,666539 sq mi1841
61Massac CountyMetropolis15,429239 sq mi1843
62McDonough CountyMacomb32,612589 sq mi1826
63McHenry CountyWoodstock308,760604 sq mi1836
64McLean CountyBloomington169,5721,184 sq mi1830
65Menard CountyPetersburg12,705314 sq mi1839
66Mercer CountyAledo16,434561 sq mi1825
67Monroe CountyWaterloo32,957388 sq mi1816
68Montgomery CountyHillsboro30,104704 sq mi1821
69Morgan CountyJacksonville35,547569 sq mi1823
70Moultrie CountySullivan14,846336 sq mi1843
71Ogle CountyOregon53,497759 sq mi1836
72Peoria CountyPeoria186,494620 sq mi1825
73Perry CountyPinckneyville22,350441 sq mi1827
74Piatt CountyMonticello16,729440 sq mi1841
75Pike CountyPittsfield16,430830 sq mi1821
76Pope CountyGolconda4,470371 sq mi1816
77Pulaski CountyMound City6,161201 sq mi1843
78Putnam CountyHennepin6,006160 sq mi1825
79Randolph CountyChester33,476578 sq mi1795
80Richland CountyOlney16,233360 sq mi1841
81Rock Island CountyRock Island147,546427 sq mi1831
82Saline CountyHarrisburg24,913383 sq mi1847
83Sangamon CountySpringfield197,465868 sq mi1821
84Schuyler CountyRushville7,544437 sq mi1825
85Scott CountyWinchester5,355251 sq mi1839
86Shelby CountyShelbyville22,363759 sq mi1827
87St. Clair CountyBelleville270,056664 sq mi1790
88Stark CountyToulon5,994288 sq mi1839
89Stephenson CountyFreeport47,711564 sq mi1837
90Tazewell CountyPekin135,394649 sq mi1827
91Union CountyJonesboro17,808416 sq mi1818
92Vermilion CountyDanville81,625899 sq mi1826
93Wabash CountyMount Carmel11,947224 sq mi1824
94Warren CountyMonmouth17,707543 sq mi1825
95Washington CountyNashville14,716563 sq mi1818
96Wayne CountyFairfield16,760714 sq mi1819
97White CountyCarmi14,665495 sq mi1815
98Whiteside CountyMorrison58,498685 sq mi1836
99Will CountyJoliet677,560837 sq mi1836
100Williamson CountyMarion66,357424 sq mi1839
101Winnebago CountyRockford295,266514 sq mi1836
102Woodford CountyEureka38,664528 sq mi1841