| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density (/mi²) | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Vermillion | 1 | 11,750 | 11,723 | 0.26% | 2,521 | 5 | City |
| Irene | 2 | 441 | 428 | 0.46% | 1,729 | 0 | City |
| Wakonda | 3 | 336 | 347 | -0.59% | 870 | 0 | Town |
Vermillion is the largest city in Clay County, with a population of 11,750.
Wakonda is the smallest city in Clay County, with a population of 336.
There are 3 cities in Clay County, South Dakota.