Illinois county populations
102 supported county-equivalent records in Illinois; July 1, 2025 population, 2024–2025 growth and 2025 land-area density.
Population totals use July 1, 2025 observations from PEP Vintage 2025. Change is measured since July 1, 2024. County equivalents are included, including Connecticut planning regions. Missing density is displayed as unavailable, never as zero.
Population table and filters
Whole-dataset downloads| Place | Population · 2025 | Change · 2024–25 | Growth · 2024–25 | People / sq. mi. |
|---|---|---|---|---|
| Cook CountyIllinois · County equivalent · 17031 | 5,194,625 | +5,834 | +0.11% | 5,497.4 |
| DuPage CountyIllinois · County equivalent · 17043 | 934,298 | +1,647 | +0.18% | 2,849.4 |
| Lake CountyIllinois · County equivalent · 17097 | 719,339 | +849 | +0.12% | 1,621.3 |
| Will CountyIllinois · County equivalent · 17197 | 712,253 | +3,273 | +0.46% | 852.1 |
| Kane CountyIllinois · County equivalent · 17089 | 525,757 | +2,327 | +0.44% | 1,012.3 |
| McHenry CountyIllinois · County equivalent · 17111 | 317,751 | +2,021 | +0.64% | 526.6 |
| Winnebago CountyIllinois · County equivalent · 17201 | 283,674 | +709 | +0.25% | 552.9 |
| Madison CountyIllinois · County equivalent · 17119 | 263,110 | -207 | -0.08% | 367.7 |
| St. Clair CountyIllinois · County equivalent · 17163 | 250,708 | -667 | -0.27% | 381.2 |
| Champaign CountyIllinois · County equivalent · 17019 | 209,972 | +794 | +0.38% | 210.8 |
| Sangamon CountyIllinois · County equivalent · 17167 | 194,170 | +134 | +0.07% | 223.6 |
| Peoria CountyIllinois · County equivalent · 17143 | 178,553 | +12 | +0.01% | 288.6 |
| McLean CountyIllinois · County equivalent · 17113 | 171,419 | -93 | -0.05% | 144.9 |
| Kendall CountyIllinois · County equivalent · 17093 | 145,470 | +2,345 | +1.64% | 454.2 |
| Rock Island CountyIllinois · County equivalent · 17161 | 141,869 | +278 | +0.20% | 331.9 |
| Tazewell CountyIllinois · County equivalent · 17179 | 130,049 | +67 | +0.05% | 201.2 |
| LaSalle CountyIllinois · County equivalent · 17099 | 107,773 | -102 | -0.09% | 94.9 |
| Kankakee CountyIllinois · County equivalent · 17091 | 105,525 | -289 | -0.27% | 156.0 |
| DeKalb CountyIllinois · County equivalent · 17037 | 101,835 | +1,214 | +1.21% | 161.3 |
| Macon CountyIllinois · County equivalent · 17115 | 99,300 | -649 | -0.65% | 171.0 |
| Vermilion CountyIllinois · County equivalent · 17183 | 71,259 | -197 | -0.28% | 79.3 |
| Williamson CountyIllinois · County equivalent · 17199 | 67,225 | +151 | +0.23% | 160.0 |
| Adams CountyIllinois · County equivalent · 17001 | 64,267 | +51 | +0.08% | 75.2 |
| Whiteside CountyIllinois · County equivalent · 17195 | 54,121 | -302 | -0.55% | 79.1 |
| Grundy CountyIllinois · County equivalent · 17063 | 54,052 | +331 | +0.62% | 129.3 |
| Boone CountyIllinois · County equivalent · 17007 | 53,568 | +42 | +0.08% | 190.8 |
| Jackson CountyIllinois · County equivalent · 17077 | 52,501 | -181 | -0.34% | 90.0 |
| Ogle CountyIllinois · County equivalent · 17141 | 51,399 | +125 | +0.24% | 67.8 |
| Henry CountyIllinois · County equivalent · 17073 | 48,095 | -98 | -0.20% | 58.4 |
| Knox CountyIllinois · County equivalent · 17095 | 47,767 | -197 | -0.41% | 66.7 |
| Coles CountyIllinois · County equivalent · 17029 | 46,607 | +34 | +0.07% | 91.7 |
| Macoupin CountyIllinois · County equivalent · 17117 | 43,748 | -169 | -0.38% | 50.7 |
| Stephenson CountyIllinois · County equivalent · 17177 | 43,220 | -202 | -0.47% | 76.6 |
| Woodford CountyIllinois · County equivalent · 17203 | 38,111 | -87 | -0.23% | 72.2 |
| Clinton CountyIllinois · County equivalent · 17027 | 37,128 | +40 | +0.11% | 78.3 |
| Franklin CountyIllinois · County equivalent · 17055 | 36,916 | -38 | -0.10% | 90.3 |
| Marion CountyIllinois · County equivalent · 17121 | 36,382 | -119 | -0.33% | 63.5 |
| Jefferson CountyIllinois · County equivalent · 17081 | 36,147 | +35 | +0.10% | 63.3 |
| Livingston CountyIllinois · County equivalent · 17105 | 35,057 | -127 | -0.36% | 33.6 |
| Monroe CountyIllinois · County equivalent · 17133 | 34,840 | -265 | -0.75% | 90.4 |
| Effingham CountyIllinois · County equivalent · 17049 | 34,519 | -22 | -0.06% | 72.1 |
| Christian CountyIllinois · County equivalent · 17021 | 33,443 | +1 | +0.00% | 47.1 |
| Lee CountyIllinois · County equivalent · 17103 | 32,914 | +63 | +0.19% | 45.4 |
| Fulton CountyIllinois · County equivalent · 17057 | 32,901 | +94 | +0.29% | 38.0 |
| Morgan CountyIllinois · County equivalent · 17137 | 32,515 | -124 | -0.38% | 57.1 |
| Bureau CountyIllinois · County equivalent · 17011 | 32,510 | -9 | -0.03% | 37.4 |
| Randolph CountyIllinois · County equivalent · 17157 | 29,921 | +51 | +0.17% | 52.0 |
| Montgomery CountyIllinois · County equivalent · 17135 | 28,076 | +239 | +0.86% | 39.9 |
| Logan CountyIllinois · County equivalent · 17107 | 27,182 | -37 | -0.14% | 44.0 |
| Iroquois CountyIllinois · County equivalent · 17075 | 26,150 | -72 | -0.27% | 23.4 |
Use these comparisons consistently
A larger population does not necessarily mean faster growth. Absolute change measures the number of residents gained or lost; percentage change divides that difference by the starting population. The percentage column here covers one July-to-July interval, rather than a decade or a partial calendar year. Percent growth is suppressed where the starting population is zero.
Density divides the unrounded July 1, 2025 population by matching 2025 Gazetteer land area. It is measured in people per square mile and excludes water area. These geographic averages depend on the size and definition of each unit, so a county’s density is not directly comparable to a built-up city neighborhood.
County-equivalent names and units vary by state. Connecticut planning regions are represented in the current series; linking older county series requires a documented relationship. Incorporated places may cross county boundaries and do not form an exhaustive county breakdown.
Exports contain the current page’s visible rows after filtering, with reference date and release metadata. Use whole-dataset downloads for every row or select a compatible comparison to inspect a longer interval. The initial pep-2025-r1 snapshot remains reproducible when future releases are added.