4 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Fort Thompson | 1 | 1,126 | 1,275 | -0.88% | 109 | 10.38 | CDP |
| Millerdale Colony | 2 | 108 | 16 | 8% | 420 | 0.26 | CDP |
| Elvira township | 3 | 46 | 45 | 2.22% | 1 | 47.66 | Township |
| Gann Valley | 4 | 15 | 11 | 7.14% | 190 | 0.08 | CDP |
Fort Thompson is the largest city in Buffalo County, with a population of 1,126.
Gann Valley is the smallest city in Buffalo County.
There are 4 cities in Buffalo County, South Dakota.