Illinois Population By County in 2018
Updated on January 29, 2024.
According to the US Census Bureau population estimates, there were 12,724,685 people living in Illinois in 2018. Cook County was the most populated county with 5,171,007 residents, followed by DuPage County with 927,808 residents, and Lake County with 700,455 residents. Hardin County with a population of 3,876 was the least populated county in Illinois in 2018.
Use the map below to interactively explore the population for each county in Illinois in 2018. The data can also be explored further by sorting and filtering with the table below.
You can see similar information for other states and by state for the United States.
Related Topics: Illinois Census Vintage Data Topic List.
Data Source: US Census Bureau (Vintage).
See this for other years:
Illinois Population By County in 2018
Table of Illinois Population By County in 2018
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| County | Population | % of State Population |
|---|---|---|
| Adams | 65,603 | 0.52% |
| Alexander | 6,043 | 0.05% |
| Bond | 16,668 | 0.13% |
| Boone | 53,368 | 0.42% |
| Brown | 6,580 | 0.05% |
| Bureau | 32,938 | 0.26% |
| Calhoun | 4,834 | 0.04% |
| Carroll | 14,337 | 0.11% |
| Cass | 12,353 | 0.10% |
| Champaign | 210,206 | 1.65% |
| Christian | 32,709 | 0.26% |
| Clark | 15,594 | 0.12% |
| Clay | 13,260 | 0.10% |
| Clinton | 37,666 | 0.30% |
| Coles | 50,946 | 0.40% |
| Cook | 5,171,007 | 40.64% |
| Crawford | 18,849 | 0.15% |
| Cumberland | 10,782 | 0.09% |
| DeKalb | 104,587 | 0.82% |
| De Witt | 15,768 | 0.12% |
| Douglas | 19,449 | 0.15% |
| DuPage | 927,808 | 7.29% |
| Edgar | 17,379 | 0.14% |
| Edwards | 6,393 | 0.05% |
| Effingham | 34,233 | 0.27% |
| Fayette | 21,380 | 0.17% |
| Ford | 13,215 | 0.10% |
| Franklin | 38,737 | 0.30% |
| Fulton | 34,743 | 0.27% |
| Gallatin | 5,049 | 0.04% |
| Greene | 13,051 | 0.10% |
| Grundy | 51,012 | 0.40% |
| Hamilton | 8,149 | 0.06% |
| Hancock | 17,815 | 0.14% |
| Hardin | 3,876 | 0.03% |
| Henderson | 6,726 | 0.05% |
| Henry | 49,082 | 0.39% |
| Iroquois | 27,450 | 0.22% |
| Jackson | 57,327 | 0.45% |
| Jasper | 9,589 | 0.08% |
| Jefferson | 37,704 | 0.30% |
| Jersey | 21,738 | 0.17% |
| Jo Daviess | 21,349 | 0.17% |
| Johnson | 12,380 | 0.10% |
| Kane | 532,838 | 4.19% |
| Kankakee | 109,863 | 0.86% |
| Kendall | 127,663 | 1.00% |
| Knox | 50,008 | 0.39% |
| Lake | 700,455 | 5.51% |
| LaSalle | 109,136 | 0.86% |
| Lawrence | 15,816 | 0.12% |
| Lee | 34,281 | 0.27% |
| Livingston | 35,630 | 0.28% |
| Logan | 28,873 | 0.23% |
| McDonough | 30,091 | 0.24% |
| McHenry | 308,145 | 2.42% |
| McLean | 172,368 | 1.36% |
| Macon | 104,529 | 0.82% |
| Macoupin | 45,342 | 0.36% |
| Madison | 264,481 | 2.08% |
| Marion | 37,453 | 0.29% |
| Marshall | 11,485 | 0.09% |
| Mason | 13,520 | 0.11% |
| Massac | 14,037 | 0.11% |
| Menard | 12,297 | 0.10% |
| Mercer | 15,572 | 0.12% |
| Monroe | 34,446 | 0.27% |
| Montgomery | 28,705 | 0.23% |
| Morgan | 34,052 | 0.27% |
| Moultrie | 14,662 | 0.12% |
| Ogle | 50,802 | 0.40% |
| Peoria | 180,773 | 1.42% |
| Perry | 21,163 | 0.17% |
| Piatt | 16,375 | 0.13% |
| Pike | 15,614 | 0.12% |
| Pope | 4,183 | 0.03% |
| Pulaski | 5,426 | 0.04% |
| Putnam | 5,740 | 0.05% |
| Randolph | 32,161 | 0.25% |
| Richland | 15,700 | 0.12% |
| Rock Island | 142,522 | 1.12% |
| St. Clair | 261,631 | 2.06% |
| Saline | 23,769 | 0.19% |
| Sangamon | 195,802 | 1.54% |
| Schuyler | 6,896 | 0.05% |
| Scott | 4,952 | 0.04% |
| Shelby | 21,685 | 0.17% |
| Stark | 5,407 | 0.04% |
| Stephenson | 44,702 | 0.35% |
| Tazewell | 132,465 | 1.04% |
| Union | 16,853 | 0.13% |
| Vermilion | 76,703 | 0.60% |
| Wabash | 11,407 | 0.09% |
| Warren | 16,979 | 0.13% |
| Washington | 14,010 | 0.11% |
| Wayne | 16,311 | 0.13% |
| White | 13,642 | 0.11% |
| Whiteside | 55,532 | 0.44% |
| Will | 690,934 | 5.43% |
| Williamson | 67,017 | 0.53% |
| Winnebago | 283,588 | 2.23% |
| Woodford | 38,461 | 0.30% |