29 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Rapid City | 1 | 82,388 | 74,928 | 1.84% | 1,496 | 55.07 | City |
| Box Elder | 2 | 15,156 | 11,935 | 4.44% | 1,027 | 14.75 | City |
| Rapid Valley | 3 | 7,090 | 8,553 | -1.09% | 1,096 | 6.47 | CDP |
| Green Valley | 4 | 1,459 | 1,252 | 2.46% | 380 | 3.84 | CDP |
| Hill City | 5 | 1,003 | 877 | 2.56% | 764 | 1.31 | City |
| Wall | 6 | 681 | 698 | -0.44% | 259 | 2.63 | Town |
| New Underwood | 7 | 621 | 593 | 0.98% | 426 | 1.46 | City |
| Keystone | 8 | 239 | 244 | -0.42% | 80 | 3 | Town |
| Quinn | 9 | 64 | 63 | 0% | 53 | 1.20 | Town |
| Wasta | 10 | 61 | 63 | 0% | 318 | 0.19 | Town |
| Scenic township | 11 | 56 | 55 | 0% | 0.00 | 134.05 | Township |
| Cedar Butte township | 12 | 41 | 42 | -2.38% | 1 | 35.43 | Township |
| Lake Creek township | 13 | 38 | 39 | -2.56% | 1 | 35.85 | Township |
| Lake Hill township | 14 | 36 | 39 | -2.7% | 1 | 35.11 | Township |
| Owanka township | 15 | 35 | 32 | 2.94% | 1 | 50.71 | Township |
| Wasta township | 16 | 35 | 35 | 0% | 1 | 35.78 | Township |
| Lake Flat township | 17 | 34 | 31 | 3.03% | 1 | 34.43 | Township |
| Peno township | 18 | 33 | 33 | 0% | 1 | 35.77 | Township |
| Castle Butte township | 19 | 32 | 32 | 0% | 1 | 51.02 | Township |
| Crooked Creek township | 20 | 23 | 23 | 0% | 0.00 | 71.12 | Township |
| Ash township | 21 | 22 | 22 | 0% | 1 | 43.83 | Township |
| Rainy Creek/Cheyenne township | 22 | 20 | 20 | 0% | 0.00 | 91.33 | Township |
| Sunnyside township | 23 | 15 | 15 | 0% | 0.00 | 38.86 | Township |
| Shyne township | 24 | 12 | 12 | 0% | 0.00 | 26.89 | Township |
| Wall township | 25 | 11 | 11 | 0% | 0.00 | 33.22 | Township |
| Quinn township | 26 | 11 | 11 | 0% | 0.00 | 34.26 | Township |
| Conata township | 27 | 10 | 10 | 0% | 0.00 | 89.37 | Township |
| Imlay township | 28 | 9 | 9 | 0% | 0.00 | 110.42 | Township |
| Flat Butte township | 29 | 7 | 7 | 0% | 0.00 | 35.47 | Township |
Rapid City is the largest city in Pennington County, with a population of 82,388.
Flat Butte township is the smallest city in Pennington County.
There are 29 cities in Pennington County, South Dakota.