27 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Rapid City | 1 | 81,131 | 74,943 | 1.55% | 1,449 | 56 | City |
| Box Elder | 2 | 14,372 | 11,946 | 3.49% | 974 | 15 | City |
| Hill City | 3 | 952 | 875 | 1.6% | 726 | 1 | City |
| Wall | 4 | 665 | 698 | -1.04% | 253 | 3 | Town |
| New Underwood | 5 | 611 | 605 | 0.16% | 367 | 2 | City |
| Keystone | 6 | 265 | 244 | 1.53% | 88 | 3 | Town |
| Wasta | 7 | 62 | 65 | -1.59% | 323 | 0 | Town |
| Quinn | 8 | 60 | 62 | -1.64% | 50 | 1 | Town |
| Scenic | 9 | 54 | 55 | -1.82% | 0.00 | 134 | Township |
| Lake Hill | 10 | 44 | 41 | 4.76% | 1 | 35 | Township |
| Cedar Butte | 11 | 42 | 43 | -2.33% | 1 | 35 | Township |
| Lake Creek | 12 | 39 | 40 | -2.5% | 1 | 36 | Township |
| Peno | 13 | 33 | 31 | 3.13% | 1 | 36 | Township |
| Wasta | 14 | 32 | 34 | -3.03% | 1 | 36 | Township |
| Lake Flat | 15 | 31 | 32 | -3.13% | 1 | 34 | Township |
| Owanka | 16 | 30 | 31 | -3.23% | 1 | 51 | Township |
| Castle Butte | 17 | 28 | 30 | -3.45% | 1 | 51 | Township |
| Crooked Creek | 18 | 23 | 23 | -4.17% | 0.00 | 71 | Township |
| Rainy Creek/Cheyenne | 19 | 20 | 18 | 5.26% | 0.00 | 91 | Township |
| Ash | 20 | 19 | 21 | -5% | 0.00 | 44 | Township |
| Sunnyside | 21 | 13 | 15 | -7.14% | 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 81,131.
Flat Butte is the smallest city in Pennington County, with a population of 7.
There are 27 cities in Pennington County, South Dakota.