15 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| White River | 1 | 506 | 535 | -1.17% | 971 | 1 | City |
| Norris | 2 | 167 | 177 | -1.18% | 8 | 21 | Township |
| Blackpipe | 3 | 45 | 48 | 0% | 1 | 36 | Township |
| Wood | 4 | 41 | 44 | -2.38% | 167 | 0 | Town |
| Bad Nation | 5 | 30 | 32 | 0% | 0.00 | 72 | Township |
| Mosher | 6 | 27 | 29 | 0% | 1 | 36 | Township |
| Cody | 7 | 23 | 24 | 0% | 0.00 | 74 | Township |
| Running Bird | 8 | 20 | 21 | 0% | 1 | 36 | Township |
| Red Fish | 9 | 17 | 18 | 0% | 0.00 | 43 | Township |
| Riverside | 10 | 16 | 17 | 0% | 0.00 | 56 | Township |
| Surprise Valley | 11 | 15 | 14 | 0% | 0.00 | 34 | Township |
| New Surprise Valley | 12 | 6 | 6 | 0% | 0.00 | 36 | Township |
| Rocky Ford | 13 | 6 | 8 | -14.29% | 0.00 | 50 | Township |
| Butte | 14 | 2 | 2 | 0% | 0.00 | 37 | Township |
| Prospect | 15 | 1 | 1 | 0% | 0.00 | 86 | Township |
White River is the largest city in Mellette County, with a population of 506.
Prospect is the smallest city in Mellette County, with a population of 1.
There are 15 cities in Mellette County, South Dakota.