The graph below ranks each Illinois County by total residents according to the 2012 census estimates.
Illinois total population by county
| County | Total Population |
| Cook |  5,227,992 |
| DuPage | 927,418 |
| Lake | 701,219 |
| Will | 681,590 |
| Kane | 521,306 |
| McHenry | 307,729 |
| Winnebago | 291,844 |
| St. Clair | 268,714 |
| Madison | 267,899 |
| Champaign | 203,435 |
| Sangamon | 199,269 |
| Peoria | 187,255 |
| McLean | 172,295 |
| Rock Island | 147,514 |
| Tazewell | 136,122 |
| Kendall | 118,108 |
| La Salle | 112,944 |
| Kankakee | 112,847 |
| Macon | 109,978 |
| DeKalb | 104,622 |
| Vermilion | 80,715 |
| Adams | 67,243 |
| Williamson | 66,714 |
| Jackson | 60,113 |
| Whiteside | 57,832 |
| Boone | 53,859 |
| Coles | 53,659 |
| Ogle | 52,850 |
| Knox | 52,254 |
| Grundy | 50,208 |
| Henry | 50,177 |
| Macoupin | 47,205 |
| Stephenson | 46,943 |
| Franklin | 39,482 |
| Woodford | 38,965 |
| Marion | 38,868 |
| Jefferson | 38,677 |
| Livingston | 38,525 |
| Clinton | 38,083 |
| Fulton | 36,673 |
| Morgan | 35,309 |
| Lee | 35,132 |
| Christian | 34,597 |
| Effingham | 34,335 |
| Bureau | 34,314 |
| Monroe | 33,310 |
| Randolph | 32,956 |
| McDonough | 32,572 |
| Logan | 30,027 |
| Montgomery | 29,688 |
| Iroquois | 29,257 |
| Saline | 25,007 |
| Jersey | 22,738 |
| Jo Daviess | 22,552 |
| Shelby | 22,205 |
| Perry | 22,078 |
| Fayette | 22,025 |
| Douglas | 19,883 |
| Crawford | 19,605 |
| Hancock | 18,900 |
| Edgar | 18,160 |
| Warren | 17,808 |
| Union | 17,649 |
| Bond | 17,612 |
| Wayne | 16,622 |
| Lawrence | 16,592 |
| Piatt | 16,511 |
| De Witt | 16,484 |
| Clark | 16,298 |
| Pike | 16,276 |
| Mercer | 16,223 |
| Richland | 16,214 |
| Massac | 15,174 |
| Carroll | 15,047 |
| Moultrie | 14,946 |
| Washington | 14,640 |
| White | 14,584 |
| Mason | 14,372 |
| Ford | 13,997 |
| Clay | 13,746 |
| Greene | 13,622 |
| Cass | 13,421 |
| Johnson | 12,786 |
| Menard | 12,704 |
| Marshall | 12,315 |
| Wabash | 11,746 |
| Cumberland | 10,977 |
| Jasper | 9,656 |
| Hamilton | 8,386 |
| Alexander | 7,752 |
| Schuyler | 7,490 |
| Henderson | 7,062 |
| Brown | 6,908 |
| Edwards | 6,724 |
| Pulaski | 5,960 |
| Stark | 5,948 |
| Putnam | 5,876 |
| Gallatin | 5,439 |
| Scott | 5,282 |
| Calhoun | 5,021 |
| Pope | 4,271 |
| Hardin | 4,256 |