The largest county in Missouri
There are two right answers. By land area it is Texas County; by population it is St. Louis 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 | Texas County | 1,177 sq mi | 25,994 |
| 2 | Shannon County | 1,004 sq mi | 7,285 |
| 3 | Howell County | 927.2 sq mi | 40,798 |
| 4 | Franklin County | 922.5 sq mi | 108,090 |
| 5 | Nodaway County | 877 sq mi | 20,174 |
| 6 | Bates County | 836.7 sq mi | 16,512 |
| 7 | Callaway County | 834.6 sq mi | 45,765 |
| 8 | Johnson County | 829.3 sq mi | 56,670 |
| 9 | Vernon County | 826.4 sq mi | 19,946 |
| 10 | Stoddard County | 823.1 sq mi | 28,284 |
By population
| Rank | Name | Population | Density |
|---|---|---|---|
| 1 | St. Louis County | 990,911 | 1,949 per sq mi |
| 2 | Jackson County | 732,994 | 1,213 per sq mi |
| 3 | St. Charles County | 426,499 | 761 per sq mi |
| 4 | Greene County | 309,286 | 458 per sq mi |
| 5 | St. Louis city | 278,144 | 4,507 per sq mi |
| 6 | Clay County | 265,032 | 666 per sq mi |
| 7 | Jefferson County | 233,132 | 355 per sq mi |
| 8 | Boone County | 191,746 | 280 per sq mi |
| 9 | Jasper County | 127,428 | 200 per sq mi |
| 10 | Cass County | 115,859 | 166 per sq mi |
And the smallest
More on Missouri
Rebuilt from source data 30 August 2026. How these figures are produced.