The largest county in Indiana
There are two right answers. By land area it is Allen County; by population it is Marion County. Which one you want depends on what you meant by largest.
Sources: US Census Bureau, Population Estimates Program, Vintage 2025 Population Estimates, released 26 March 2026; US Census Bureau, Gazetteer Files, 2025 Gazetteer Files, released 10 September 2025. Retrieved 30 August 2026.
By land area
| Rank | Name | Land area | Population |
|---|---|---|---|
| 1 | Allen County | 657.1 sq mi | 402,329 |
| 2 | LaPorte County | 598.3 sq mi | 111,294 |
| 3 | Jasper County | 559.7 sq mi | 33,894 |
| 4 | Greene County | 542.5 sq mi | 31,165 |
| 5 | Kosciusko County | 531.4 sq mi | 80,892 |
| 6 | Knox County | 515.8 sq mi | 35,652 |
| 7 | Washington County | 513.7 sq mi | 28,383 |
| 8 | Jackson County | 510 sq mi | 47,370 |
| 9 | White County | 505.2 sq mi | 25,164 |
| 10 | Montgomery County | 504.6 sq mi | 38,954 |
By population
| Rank | Name | Population | Density |
|---|---|---|---|
| 1 | Marion County | 992,196 | 2,506 per sq mi |
| 2 | Lake County | 504,612 | 1,011 per sq mi |
| 3 | Allen County | 402,329 | 612 per sq mi |
| 4 | Hamilton County | 387,036 | 981 per sq mi |
| 5 | St. Joseph County | 272,861 | 596 per sq mi |
| 6 | Elkhart County | 208,774 | 451 per sq mi |
| 7 | Hendricks County | 193,510 | 476 per sq mi |
| 8 | Tippecanoe County | 190,456 | 382 per sq mi |
| 9 | Vanderburgh County | 181,995 | 780 per sq mi |
| 10 | Porter County | 176,049 | 421 per sq mi |
And the smallest
More on Indiana
Rebuilt from source data 30 August 2026. How these figures are produced.