| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density (/mi²) | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Iola | 1 | 5,210 | 5,402 | -0.57% | 1,122 | 5 | City |
| Humboldt | 2 | 1,797 | 1,847 | -0.55% | 1,177 | 2 | City |
| La Harpe | 3 | 481 | 485 | 0% | 604 | 1 | City |
| Gas | 4 | 466 | 473 | -0.21% | 647 | 1 | City |
| Moran | 5 | 453 | 465 | -0.44% | 1,081 | 0 | City |
| Savonburg | 6 | 75 | 75 | 0% | 391 | 0 | City |
| Earlton | 7 | 59 | 59 | -1.67% | 369 | 0 | City |
| Elsmore | 8 | 51 | 53 | -1.92% | 336 | 0 | City |
| Lone Elm | 9 | 22 | 22 | 0% | 324 | 0 | City |
| Bassett | 10 | 20 | 21 | 0% | 299 | 0 | City |
Iola is the largest city in Allen County, with a population of 5,210.
Bassett is the smallest city in Allen County, with a population of 20.
There are 10 cities in Allen County, Kansas.