8 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 |
Rapid City is the largest city in Pennington County, with a population of 82,369.
Quinn is the smallest city in Pennington County, with a population of 60.
There are 8 cities in Pennington County, South Dakota.