21 cities
| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Iola | 1 | 5,264 | 5,398 | -0.42% | 1,134 | 5 | City |
| Humboldt | 2 | 1,802 | 1,847 | -0.39% | 1,180 | 2 | City |
| Elm | 3 | 1,173 | 1,177 | -0.09% | 25 | 47 | Township |
| Iola | 4 | 786 | 786 | 0.13% | 18 | 43 | Township |
| Marmaton | 5 | 742 | 754 | -0.54% | 13 | 56 | Township |
| La Harpe | 6 | 489 | 485 | 0.2% | 614 | 1 | City |
| Gas | 7 | 463 | 471 | -0.22% | 643 | 1 | City |
| Moran | 8 | 461 | 467 | -0.22% | 1,100 | 0 | City |
| Elsmore | 9 | 354 | 353 | 0% | 6 | 64 | Township |
| Carlyle | 10 | 291 | 288 | 0.34% | 10 | 30 | Township |
| Humboldt | 11 | 268 | 271 | -0.37% | 11 | 25 | Township |
| Osage | 12 | 263 | 261 | 0% | 5 | 48 | Township |
| Salem | 13 | 249 | 246 | 0.4% | 5 | 48 | Township |
| Cottage Grove | 14 | 222 | 221 | -0.45% | 6 | 37 | Township |
| Geneva | 15 | 143 | 136 | 1.42% | 5 | 30 | Township |
| Deer Creek | 16 | 104 | 105 | -0.95% | 3 | 36 | Township |
| Savonburg | 17 | 76 | 75 | 0% | 396 | 0 | City |
| Earlton | 18 | 57 | 59 | 0% | 356 | 0 | City |
| Elsmore | 19 | 51 | 53 | 0% | 336 | 0 | City |
| Bassett | 20 | 22 | 22 | 0% | 328 | 0 | City |
| Lone Elm | 21 | 22 | 22 | 0% | 324 | 0 | City |
Iola is the largest city in Allen County, with a population of 5,264.
Lone Elm is the smallest city in Allen County, with a population of 22.
There are 21 cities in Allen County, Kansas.