| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density (/mi²) | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Chariton | 1 | 4,378 | 4,185 | 0.71% | 1,162 | 4 | City |
| Russell | 2 | 478 | 472 | 0.21% | 466 | 1 | City |
| Lucas | 3 | 178 | 174 | 0.56% | 181 | 1 | City |
| Williamson | 4 | 130 | 118 | 1.56% | 341 | 0 | City |
| Derby | 5 | 90 | 89 | 0% | 353 | 0 | City |
Chariton is the largest city in Lucas County, with a population of 4,378.
Derby is the smallest city in Lucas County, with a population of 90.
There are 5 cities in Lucas County, Iowa.