Illinois Population By County in 2021

Updated on August 1, 2024.

Based on the US Census Vintage data estimates, in 2021, the population of Illinois was 12,690,341. Among all Illinois counties, Cook had the highest population (5,180,919), followed by DuPage (926,848), and Lake (712,570). Hardin was the least populated county (3,635).

Hover over or click on the counties in the map below to see the populations. The data can also be found in a table below. You can use the table to sort, filter, and explore the data further.

You can see similar information for other states and by state for the United States.

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Illinois Population By County in 2021
Illinois Population By County in 2021
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County Population % of State Population
Adams 65064 0.51
Alexander 5025 0.04
Bond 16623 0.13
Boone 53173 0.42
Brown 6432 0.05
Bureau 32959 0.26
Calhoun 4395 0.04
Carroll 15702 0.12
Cass 12790 0.10
Champaign 206605 1.63
Christian 33703 0.27
Clark 15352 0.12
Clay 13163 0.10
Clinton 36882 0.29
Coles 46802 0.37
Cook 5180919 40.83
Crawford 18684 0.15
Cumberland 10352 0.08
DeKalb 100482 0.79
De Witt 15403 0.12
Douglas 19694 0.16
DuPage 926848 7.30
Edgar 16576 0.13
Edwards 6084 0.05
Effingham 34508 0.27
Fayette 21438 0.17
Ford 13479 0.11
Franklin 37459 0.30
Fulton 33275 0.26
Gallatin 4895 0.04
Greene 11847 0.09
Grundy 52959 0.42
Hamilton 7913 0.06
Hancock 17376 0.14
Hardin 3635 0.03
Henderson 6306 0.05
Henry 48911 0.39
Iroquois 26775 0.21
Jackson 52604 0.42
Jasper 9193 0.07
Jefferson 36889 0.29
Jersey 21349 0.17
Jo Daviess 21972 0.17
Johnson 13472 0.11
Kane 516292 4.07
Kankakee 106605 0.84
Kendall 135015 1.06
Knox 49310 0.39
Lake 712570 5.62
LaSalle 109160 0.86
Lawrence 15228 0.12
Lee 34195 0.27
Livingston 35769 0.28
Logan 27979 0.22
McDonough 26880 0.21
McHenry 311543 2.46
McLean 171109 1.35
Macon 102597 0.81
Macoupin 44492 0.35
Madison 264867 2.09
Marion 37379 0.30
Marshall 11668 0.09
Mason 12830 0.10
Massac 13946 0.11
Menard 12167 0.10
Mercer 15580 0.12
Monroe 35004 0.28
Montgomery 28082 0.22
Morgan 32646 0.26
Moultrie 14561 0.12
Ogle 51464 0.41
Peoria 179638 1.42
Perry 21014 0.17
Piatt 16757 0.13
Pike 14621 0.12
Pope 3758 0.03
Pulaski 5075 0.04
Putnam 5588 0.04
Randolph 30204 0.24
Richland 15767 0.12
Rock Island 142923 1.13
St. Clair 254958 2.01
Saline 23316 0.18
Sangamon 195371 1.54
Schuyler 6831 0.05
Scott 4849 0.04
Shelby 20862 0.16
Stark 5284 0.04
Stephenson 44062 0.35
Tazewell 130412 1.03
Union 16921 0.13
Vermilion 73164 0.58
Wabash 11208 0.09
Warren 16585 0.13
Washington 13640 0.11
Wayne 15956 0.13
White 13758 0.11
Whiteside 55302 0.44
Will 699176 5.51
Williamson 66883 0.53
Winnebago 283333 2.23
Woodford 38220 0.30