6 cities
| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Flora | 1 | 4,573 | 4,795 | -0.8% | 975 | 5 | City |
| Louisville | 2 | 1,088 | 1,144 | -0.82% | 1,314 | 1 | Village |
| Clay City | 3 | 802 | 853 | -0.99% | 450 | 2 | Village |
| Xenia | 4 | 363 | 384 | -0.82% | 736 | 0 | Village |
| Iola | 5 | 94 | 100 | -1.05% | 98 | 1 | Village |
| Sailor Springs | 6 | 89 | 94 | -1.11% | 342 | 0 | Village |
Flora is the largest city in Clay County, with a population of 4,573.
Sailor Springs is the smallest city in Clay County, with a population of 89.
There are 6 cities in Clay County, Illinois.