27 cities
| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Rapid City | 1 | 82,369 | 74,943 | 1.53% | 1,471 | 56 | City |
| Box Elder | 2 | 14,857 | 11,946 | 3.37% | 1,007 | 15 | City |
| Hill City | 3 | 968 | 875 | 1.68% | 738 | 1 | City |
| Wall | 4 | 659 | 698 | -0.9% | 251 | 3 | Town |
| New Underwood | 5 | 612 | 605 | 0.16% | 368 | 2 | City |
| Keystone | 6 | 269 | 244 | 1.51% | 90 | 3 | Town |
| Wasta | 7 | 62 | 65 | 0% | 323 | 0 | Town |
| Quinn | 8 | 60 | 62 | 0% | 50 | 1 | Town |
| Scenic | 9 | 53 | 55 | -1.85% | 0.00 | 134 | Township |
| Lake Hill | 10 | 46 | 41 | 4.55% | 1 | 35 | Township |
| Cedar Butte | 11 | 41 | 43 | -2.38% | 1 | 35 | Township |
| Lake Creek | 12 | 38 | 40 | -2.56% | 1 | 36 | Township |
| Peno | 13 | 34 | 31 | 3.03% | 1 | 36 | Township |
| Wasta | 14 | 31 | 34 | -3.13% | 1 | 36 | Township |
| Lake Flat | 15 | 30 | 32 | -3.23% | 1 | 34 | Township |
| Owanka | 16 | 29 | 31 | -3.33% | 1 | 51 | Township |
| Castle Butte | 17 | 27 | 30 | -3.57% | 1 | 51 | Township |
| Crooked Creek | 18 | 22 | 23 | -4.35% | 0.00 | 71 | Township |
| Rainy Creek/Cheyenne | 19 | 21 | 18 | 5% | 0.00 | 91 | Township |
| Ash | 20 | 18 | 21 | -5.26% | 0.00 | 44 | Township |
| Sunnyside | 21 | 12 | 15 | -7.69% | 0.00 | 39 | Township |
| Wall | 22 | 11 | 11 | 0% | 0.00 | 33 | Township |
| Quinn | 23 | 11 | 11 | 0% | 0.00 | 34 | Township |
| Shyne | 24 | 11 | 11 | 0% | 0.00 | 27 | Township |
| Conata | 25 | 9 | 9 | 0% | 0.00 | 89 | Township |
| Imlay | 26 | 9 | 9 | 0% | 0.00 | 110 | Township |
| Flat Butte | 27 | 7 | 7 | 0% | 0.00 | 35 | Township |
Rapid City is the largest city in Pennington County, with a population of 82,369.
Flat Butte is the smallest city in Pennington County, with a population of 7.
There are 27 cities in Pennington County, South Dakota.