| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density (/mi²) | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Aberdeen | 1 | 27,857 | 28,424 | -0.37% | 1,687 | 17 | City |
| Groton | 2 | 1,327 | 1,383 | -0.75% | 758 | 2 | City |
| Warner | 3 | 443 | 473 | -1.34% | 1,588 | 0 | Town |
| Frederick | 4 | 203 | 212 | -0.98% | 150 | 1 | Town |
| Hecla | 5 | 188 | 198 | -1.05% | 547 | 0 | City |
| Columbia | 6 | 154 | 157 | -0.65% | 102 | 2 | City |
| Claremont | 7 | 106 | 109 | -0.93% | 422 | 0 | Town |
| Westport | 8 | 80 | 85 | -1.23% | 340 | 0 | Town |
| Stratford | 9 | 57 | 59 | -1.72% | 228 | 0 | Town |
| Wetonka | 10 | 13 | 15 | -7.14% | 53 | 0 | Town |
| Verdon | 11 | 6 | 6 | 0% | 24 | 0 | Town |
Aberdeen is the largest city in Brown County, with a population of 27,857.
Verdon is the smallest city in Brown County, with a population of 6.
There are 11 cities in Brown County, South Dakota.