Illinois Population By County in 2018
Updated on June 22, 2021.

According to the US Census Bureau population estimates, there were 12,723,071 people living in Illinois in 2018. Cook County was the most populated county with 5,171,960 residents, followed by DuPage County with 927,247 residents, and Lake County with 699,587 residents. Hardin County with a population of 3,893 was the least populated county in Illinois in 2018.

Use the map below to interactively explore the population of each county in Illinois in 2018. The data can also be explored further by sorting and filtering with the table below.

Hover/Click on the counties to see the values.
Illinois Population By County in 2018
See also Population estimate for other years:
Table of Illinois Population By County in 2018
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County Population % of State Population
Adams 65,623 0.52%
Alexander 6,041 0.05%
Bond 16,637 0.13%
Boone 53,480 0.42%
Brown 6,563 0.05%
Bureau 32,959 0.26%
Calhoun 4,829 0.04%
Carroll 14,314 0.11%
Cass 12,312 0.10%
Champaign 209,918 1.65%
Christian 32,653 0.26%
Clark 15,600 0.12%
Clay 13,266 0.10%
Clinton 37,697 0.30%
Coles 50,829 0.40%
Cook 5,171,960 40.65%
Crawford 18,830 0.15%
Cumberland 10,804 0.09%
DeKalb 104,349 0.82%
De Witt 15,794 0.12%
Douglas 19,458 0.15%
DuPage 927,247 7.29%
Edgar 17,360 0.14%
Edwards 6,387 0.05%
Effingham 34,181 0.27%
Fayette 21,368 0.17%
Ford 13,212 0.10%
Franklin 38,695 0.30%
Fulton 34,830 0.27%
Gallatin 5,045 0.04%
Greene 13,065 0.10%
Grundy 50,973 0.40%
Hamilton 8,148 0.06%
Hancock 17,828 0.14%
Hardin 3,893 0.03%
Henderson 6,697 0.05%
Henry 49,069 0.39%
Iroquois 27,484 0.22%
Jackson 57,289 0.45%
Jasper 9,624 0.08%
Jefferson 37,708 0.30%
Jersey 21,795 0.17%
Jo Daviess 21,331 0.17%
Johnson 12,423 0.10%
Kane 532,720 4.19%
Kankakee 109,953 0.86%
Kendall 127,717 1.00%
Knox 49,978 0.39%
Lake 699,587 5.50%
LaSalle 109,159 0.86%
Lawrence 15,813 0.12%
Lee 34,296 0.27%
Livingston 35,714 0.28%
Logan 28,912 0.23%
McDonough 29,984 0.24%
McHenry 308,251 2.42%
McLean 172,410 1.36%
Macon 104,504 0.82%
Macoupin 45,318 0.36%
Madison 264,026 2.08%
Marion 37,381 0.29%
Marshall 11,483 0.09%
Mason 13,533 0.11%
Massac 14,023 0.11%
Menard 12,289 0.10%
Mercer 15,551 0.12%
Monroe 34,373 0.27%
Montgomery 28,691 0.23%
Morgan 34,027 0.27%
Moultrie 14,648 0.12%
Ogle 50,781 0.40%
Peoria 180,620 1.42%
Perry 21,144 0.17%
Piatt 16,366 0.13%
Pike 15,595 0.12%
Pope 4,184 0.03%
Pulaski 5,434 0.04%
Putnam 5,736 0.05%
Randolph 32,177 0.25%
Richland 15,695 0.12%
Rock Island 142,621 1.12%
St. Clair 261,360 2.05%
Saline 23,789 0.19%
Sangamon 195,639 1.54%
Schuyler 6,870 0.05%
Scott 4,927 0.04%
Shelby 21,726 0.17%
Stark 5,418 0.04%
Stephenson 44,797 0.35%
Tazewell 132,450 1.04%
Union 16,832 0.13%
Vermilion 76,702 0.60%
Wabash 11,523 0.09%
Warren 16,992 0.13%
Washington 13,999 0.11%
Wayne 16,326 0.13%
White 13,618 0.11%
Whiteside 55,553 0.44%
Will 691,149 5.43%
Williamson 66,982 0.53%
Winnebago 283,630 2.23%
Woodford 38,527 0.30%