7 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Flora | 1 | 4,654 | 4,796 | -0.6% | 992 | 4.69 | City |
| Louisville | 2 | 1,102 | 1,144 | -0.72% | 1,331 | 0.83 | Village |
| Clay City | 3 | 817 | 854 | -0.85% | 458 | 1.78 | Village |
| Xenia | 4 | 366 | 381 | -0.81% | 742 | 0.49 | Village |
| La Clede | 5 | 215 | 33 | 6.97% | 700 | 0.31 | CDP |
| Iola | 6 | 95 | 99 | -1.04% | 99 | 0.96 | Village |
| Sailor Springs | 7 | 87 | 91 | -1.14% | 335 | 0.26 | Village |
Flora is the largest city in Clay County, with a population of 4,654.
Sailor Springs is the smallest city in Clay County.
There are 7 cities in Clay County, Illinois.