Illinois Counties
Complete list of all 102 counties in Illinois with population, area, median income, and county seats — plus a free printable blank map.
Labeled outline map of Illinois counties. Download a printable version in SVG, PNG, or PDF.
All 102 Illinois counties
| County | County Seat | Population ▼ | Area | Median Income | Cities |
|---|---|---|---|---|---|
| Cook | — | 5,192,497 | 945 mi² | $87,558 | 97 |
| DuPage | — | 997,889 | 328 mi² | $117,603 | 32 |
| Lake | — | 701,818 | 444 mi² | $117,395 | 29 |
| Will | — | 697,966 | 837 mi² | $114,890 | 23 |
| Kane | — | 455,417 | 520 mi² | $109,421 | 22 |
| McHenry | — | 328,030 | 603 mi² | $106,081 | 17 |
| Winnebago | — | 285,063 | 513 mi² | $68,575 | 12 |
| Madison | — | 268,375 | 716 mi² | $79,643 | 27 |
| St. Clair | — | 247,743 | 658 mi² | $76,235 | 20 |
| Champaign | — | 208,555 | 996 mi² | $66,660 | 26 |
| Sangamon | — | 194,839 | 868 mi² | $80,354 | 20 |
| Peoria | — | 179,934 | 619 mi² | $72,442 | 17 |
| McLean | — | 171,878 | 1,183 mi² | $80,391 | 23 |
| Rock Island | — | 143,264 | 428 mi² | $69,415 | 17 |
| Kendall | — | 137,344 | 320 mi² | $107,596 | 8 |
How many counties does Illinois have?
Illinois has 102 counties covering 55,519 square miles and roughly 12,694,745 residents. The state was admitted to the Union in 1818 as the 21st state, and the current county boundaries reflect more than a century of administrative subdivision.
The largest county by land area is McLean County at 1,183 square miles, home to about 171,878 residents. The most populous is Cook County with approximately 5,192,497 residents — a density of about 5,495 people per square mile.
At the other end of the scale, Hardin County has only about 3,183 residents.
Illinois’s capital is Springfield, while the largest city is Chicago — a common pattern in the United States, where many states placed their capitals in smaller, more central towns rather than their largest commercial hubs.
Related resources
Download a printable outline of Illinois’s county boundaries from our blank map of Illinois page — available in SVG, PNG, and PDF.
Use the What County Am I In? tool to detect which Illinois county a GPS location or address falls in, or the Address to County Lookup for batch input.
For demographic radius analysis, the Find ZIP Codes in Radius and Population Within Radius tools let you draw a circle around any Illinois address and see every ZIP code and the total population inside.
Two SimpleMapLab studies cover Illinois specifically: the 100-mile radius around Springfield measures how much of the state lives within 100 miles of its capitol, and the loneliest town in Illinois ranks the state’s most isolated inhabited place. The county-counts blog post puts Illinois’s 102 counties in national context.
Frequently asked questions
Population and demographics are aggregated from ZIP-code-level US Census data via the SimpleMaps dataset. Countiesboundaries are from the US Atlas TopoJSON build of the Census Bureau’s TIGER/Line shapefiles. Land area is from the Census Gazetteer. State counts follow the US Census Bureau’s definition of counties and county-equivalents (50 states + DC = 3,143). All sources are public domain.