10 cities
| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Presho | 1 | 465 | 470 | -0.21% | 693 | 1 | City |
| Oacoma | 2 | 395 | 386 | 0.51% | 150 | 3 | Town |
| Kennebec | 3 | 288 | 278 | 0.7% | 338 | 1 | Town |
| Reliance | 4 | 128 | 125 | 0.79% | 118 | 1 | Town |
| Vivian | 5 | 125 | 123 | 0% | 3 | 36 | Township |
| Oacoma | 6 | 81 | 82 | 0% | 1 | 60 | Township |
| Iona | 7 | 65 | 65 | 0% | 1 | 128 | Township |
| Rex | 8 | 23 | 23 | 0% | 1 | 36 | Township |
| Pratt | 9 | 18 | 18 | 0% | 1 | 26 | Township |
| Bailey | 10 | 12 | 12 | 0% | 0.00 | 43 | Township |
Presho is the largest city in Lyman County, with a population of 465.
Bailey is the smallest city in Lyman County, with a population of 12.
There are 10 cities in Lyman County, South Dakota.