| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density (/mi²) | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Flora | 1 | 4,597 | 4,800 | -0.8% | 980 | 5 | City |
| Louisville | 2 | 1,099 | 1,148 | -0.81% | 1,327 | 1 | Village |
| Clay City | 3 | 808 | 850 | -0.98% | 453 | 2 | Village |
| Xenia | 4 | 356 | 375 | -1.11% | 722 | 0 | Village |
| Iola | 5 | 95 | 100 | -1.04% | 99 | 1 | Village |
| Sailor Springs | 6 | 86 | 90 | -1.15% | 331 | 0 | Village |
Flora is the largest city in Clay County, with a population of 4,597.
Sailor Springs is the smallest city in Clay County, with a population of 86.
There are 6 cities in Clay County, Illinois.