12 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Mount Sterling township | 1 | 4,296 | 4,287 | -0.3% | 116 | 37.19 | Township |
| Mount Sterling | 2 | 2,034 | 1,989 | 0.44% | 1,836 | 1.11 | City |
| Versailles township | 3 | 658 | 653 | -0.45% | 18 | 36.13 | Township |
| Versailles | 4 | 458 | 447 | 0.44% | 491 | 0.93 | Village |
| Elkhorn township | 5 | 302 | 301 | -0.66% | 8 | 37.40 | Township |
| Cooperstown township | 6 | 270 | 267 | -0.37% | 7 | 40.67 | Township |
| Pea Ridge township | 7 | 186 | 182 | 0% | 5 | 37.32 | Township |
| Missouri township | 8 | 134 | 134 | -0.74% | 4 | 35.41 | Township |
| Mound Station | 9 | 114 | 116 | 0% | 220 | 0.52 | Village |
| Buckhorn township | 10 | 81 | 80 | 0% | 2 | 37.93 | Township |
| Ripley township | 11 | 70 | 69 | 0% | 12 | 6.04 | Township |
| Ripley | 12 | 51 | 50 | 0% | 135 | 0.38 | Village |
Mount Sterling township is the largest city in Brown County, with a population of 4,296.
Ripley is the smallest city in Brown County.
There are 12 cities in Brown County, Illinois.