15 cities
| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Vermillion | 1 | 11,953 | 11,725 | 0.32% | 2,564 | 5 | City |
| Irene | 2 | 433 | 426 | 0.23% | 1,698 | 0 | City |
| Vermillion | 3 | 388 | 383 | -1.02% | 17 | 23 | Township |
| Wakonda | 4 | 341 | 346 | -0.29% | 883 | 0 | Town |
| Glenwood | 5 | 217 | 219 | -1.81% | 6 | 36 | Township |
| Meckling | 6 | 212 | 209 | -0.93% | 6 | 36 | Township |
| Spirit Mound | 7 | 203 | 204 | -1.46% | 6 | 36 | Township |
| Garfield | 8 | 193 | 193 | -1.53% | 5 | 36 | Township |
| Bethel | 9 | 188 | 183 | -0.53% | 5 | 36 | Township |
| Prairie Center | 10 | 186 | 186 | -1.59% | 5 | 36 | Township |
| Norway | 11 | 157 | 154 | -1.26% | 6 | 26 | Township |
| Pleasant Valley | 12 | 154 | 153 | -1.28% | 4 | 36 | Township |
| Riverside | 13 | 121 | 121 | -1.63% | 3 | 36 | Township |
| Star | 14 | 120 | 120 | -1.64% | 3 | 35 | Township |
| Vermillion | 15 | 87 | 83 | 1.16% | 2 | 36 | Township |
Vermillion is the largest city in Clay County, with a population of 11,953.
Vermillion is the smallest city in Clay County, with a population of 87.
There are 15 cities in Clay County, South Dakota.