Largest Counties in Illinois

Rank County Population County Seat Established Area (km2) Density
1 Cook County 5,194,664 Chicago 1831 2,450 2,120.27
2 DuPage County 916,913 Wheaton 1839 865 1,060.02
3 Lake County 703,451 Waukegan 1839 1,160 606.42
4 Will County 677,549 Joliet 1836 2,168 312.52
5 Kane County 515,258 Geneva 1836 1,349 381.96
6 McHenry County 308,749 Woodstock 1836 1,564 197.41
7 Winnebago County 295,255 Rockford 1836 1,331 221.83
8 St. Clair County 270,045 Belleville 1790 1,720 157
9 Madison County 269,271 Edwardsville 1812 1,878 143.38
10 Champaign County 201,070 Urbana 1833 2,582 77.87
11 Sangamon County 197,454 Springfield 1821 2,248 87.84
12 Peoria County 186,483 Peoria 1825 1,606 116.12
13 McLean County 169,561 Bloomington 1830 3,067 55.29
14 Rock Island County 147,535 Rock Island 1831 1,106 133.4
15 Tazewell County 135,383 Pekin 1827 1,681 80.54
16 Kendall County 114,725 Yorkville 1841 831 138.06
17 LaSalle County 113,913 Ottawa 1831 2,940 38.75
18 Kankakee County 113,438 Kankakee 1853 1,756 64.6
19 Macon County 110,757 Decatur 1829 1,505 73.59
20 DeKalb County 105,149 Sycamore 1837 1,642 64.04
21 Vermilion County 81,614 Danville 1826 2,328 35.06
22 Adams County 67,092 Quincy 1825 2,220 30.22
23 Williamson County 66,346 Marion 1839 1,098 60.42
24 Jackson County 60,207 Murphysboro 1816 1,523 39.53
25 Whiteside County 58,487 Morrison 1836 1,774 32.97
26 Boone County 54,154 Belvidere 1837 728 74.39
27 Coles County 53,862 Charleston 1830 1,316 40.93
28 Ogle County 53,486 Oregon 1836 1,966 27.21
29 Knox County 52,908 Galesburg 1825 1,854 28.54
30 Henry County 50,475 Cambridge 1825 2,132 23.67
31 Grundy County 50,052 Morris 1841 1,088 46
32 Macoupin County 47,754 Carlinville 1829 2,238 21.34
33 Stephenson County 47,700 Freeport 1837 1,461 32.65
34 Franklin County 39,550 Benton 1818 1,067 37.07
35 Marion County 39,426 Salem 1823 1,481 26.62
36 Livingston County 38,939 Pontiac 1837 2,704 14.4
37 Jefferson County 38,816 Mount Vernon 1819 1,479 26.24
38 Woodford County 38,653 Eureka 1841 1,368 28.26
39 Clinton County 37,751 Carlyle 1824 1,228 30.74
40 Fulton County 37,058 Lewistown 1823 2,243 16.52
41 Lee County 36,020 Dixon 1839 1,878 19.18
42 Morgan County 35,536 Jacksonville 1823 1,474 24.11
43 Bureau County 34,967 Princeton 1837 2,251 15.53
44 Christian County 34,789 Taylorville 1839 1,836 18.95
45 Effingham County 34,231 Effingham 1831 1,241 27.58
46 Randolph County 33,465 Chester 1795 1,497 22.35
47 Monroe County 32,946 Waterloo 1816 1,005 32.78
48 McDonough County 32,601 Macomb 1826 1,526 21.36
49 Logan County 30,294 Lincoln 1839 1,601 18.92
50 Montgomery County 30,093 Hillsboro 1821 1,823 16.51
51 Iroquois County 29,707 Watseka 1833 2,890 10.28
52 Saline County 24,902 Harrisburg 1847 992 25.1
53 Jersey County 22,974 Jerseyville 1839 956 24.03
54 Jo Daviess County 22,667 Galena 1827 1,557 14.56
55 Shelby County 22,352 Shelbyville 1827 1,966 11.37
56 Perry County 22,339 Pinckneyville 1827 1,142 19.56
57 Fayette County 22,129 Vandalia 1821 1,854 11.94
58 Douglas County 19,969 Tuscola 1859 1,080 18.49
59 Crawford County 19,806 Robinson 1816 1,150 17.22
60 Hancock County 19,093 Carthage 1825 2,059 9.27
61 Edgar County 18,565 Paris 1823 1,616 11.49
62 Union County 17,797 Jonesboro 1818 1,077 16.52
63 Bond County 17,757 Greenville 1817 984 18.05
64 Warren County 17,696 Monmouth 1825 1,406 12.59
65 Lawrence County 16,822 Lawrenceville 1821 963 17.47
66 Wayne County 16,749 Fairfield 1819 1,849 9.06
67 Piatt County 16,718 Monticello 1841 1,140 14.66
68 DeWitt County 16,550 Clinton 1839 1,031 16.05
69 Mercer County 16,423 Aledo 1825 1,453 11.3
70 Pike County 16,419 Pittsfield 1821 2,150 7.64
71 Clark County 16,324 Marshall 1819 1,300 12.56
72 Richland County 16,222 Olney 1841 932 17.41
73 Massac County 15,418 Metropolis 1843 619 24.91
74 Carroll County 15,376 Mount Carroll 1839 1,150 13.37
75 Moultrie County 14,835 Sullivan 1843 870 17.05
76 Washington County 14,705 Nashville 1818 1,458 10.09
77 Mason County 14,655 Havana 1841 1,396 10.5
78 White County 14,654 Carmi 1815 1,282 11.43
79 Ford County 14,070 Paxton 1859 1,259 11.18
80 Greene County 13,875 Carrollton 1821 1,406 9.87
81 Clay County 13,804 Louisville 1824 1,215 11.36
82 Cass County 13,631 Virginia 1837 974 13.99
83 Menard County 12,694 Petersburg 1839 813 15.61
84 Marshall County 12,629 Lacon 1839 1,000 12.63
85 Johnson County 12,571 Vienna 1812 896 14.03
86 Wabash County 11,936 Mount Carmel 1824 580 20.58
87 Cumberland County 11,037 Toledo 1843 896 12.32
88 Jasper County 9,687 Newton 1831 1,279 7.57
89 Hamilton County 8,446 McLeansboro 1821 1,127 7.49
90 Alexander County 8,227 Cairo 1819 611 13.46
91 Schuyler County 7,533 Rushville 1825 1,132 6.65
92 Henderson County 7,320 Oquawka 1841 982 7.45
93 Brown County 6,926 Mount Sterling 1839 793 8.73
94 Edwards County 6,710 Albion 1814 575 11.67
95 Pulaski County 6,150 Mound City 1843 521 11.8
96 Putnam County 5,995 Hennepin 1825 414 14.48
97 Stark County 5,983 Toulon 1839 746 8.02
98 Gallatin County 5,578 Shawneetown 1812 839 6.65
99 Scott County 5,344 Winchester 1839 650 8.22
100 Calhoun County 5,078 Hardin 1825 658 7.72
101 Pope County 4,459 Golconda 1816 961 4.64
102 Hardin County 4,309 Elizabethtown 1839 461 9.35

Largest Counties in Illinois

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