17 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Vermillion | 1 | 11,915 | 11,725 | 0.32% | 2,556 | 5 | City |
| Irene | 2 | 432 | 426 | 0.23% | 1,694 | 0 | City |
| Vermillion | 3 | 392 | 383 | -1.01% | 17 | 23 | Township |
| Wakonda | 4 | 342 | 346 | -0.29% | 886 | 0 | Town |
| Glenwood | 5 | 221 | 219 | -1.78% | 6 | 36 | Township |
| Meckling | 6 | 214 | 209 | -0.93% | 6 | 36 | Township |
| Spirit Mound | 7 | 206 | 204 | -1.44% | 6 | 36 | Township |
| Garfield | 8 | 196 | 193 | -1.51% | 5 | 36 | Township |
| Bethel | 9 | 189 | 183 | -0.53% | 5 | 36 | Township |
| Prairie Center | 10 | 189 | 186 | -1.56% | 5 | 36 | Township |
| Norway | 11 | 159 | 154 | -1.24% | 6 | 26 | Township |
| Pleasant Valley | 12 | 156 | 153 | -1.27% | 4 | 36 | Township |
| Riverside | 13 | 123 | 121 | -1.6% | 3 | 36 | Township |
| Star | 14 | 122 | 120 | -1.61% | 3 | 35 | Township |
| Burbank | 15 | 98 | 112 | 7.69% | 319 | 0 | CDP |
| Vermillion | 16 | 86 | 83 | 1.18% | 2 | 36 | Township |
| Meckling | 17 | 46 | 29 | 6.98% | 225 | 0 | CDP |
Vermillion is the largest city in Clay County, with a population of 11,915.
Meckling is the smallest city in Clay County, with a population of 46.
There are 17 cities in Clay County, South Dakota.