23 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Iola | 1 | 5,286 | 5,398 | -0.43% | 1,184 | 4 | City |
| Humboldt | 2 | 1,809 | 1,847 | -0.44% | 1,185 | 2 | City |
| Elm | 3 | 1,174 | 1,177 | -0.09% | 25 | 47 | Township |
| Iola | 4 | 785 | 786 | 0.13% | 18 | 43 | Township |
| Marmaton | 5 | 746 | 754 | -0.53% | 13 | 56 | Township |
| La Harpe | 6 | 488 | 485 | 0% | 612 | 1 | City |
| Gas | 7 | 464 | 471 | -0.43% | 644 | 1 | City |
| Moran | 8 | 462 | 467 | -0.22% | 1,103 | 0 | City |
| Elsmore | 9 | 354 | 353 | 0% | 6 | 64 | Township |
| Carlyle | 10 | 290 | 288 | 0.35% | 10 | 30 | Township |
| Humboldt | 11 | 269 | 271 | -0.37% | 11 | 25 | Township |
| Osage | 12 | 263 | 261 | 0% | 5 | 48 | Township |
| Salem | 13 | 248 | 246 | 0.4% | 5 | 48 | Township |
| Cottage Grove | 14 | 223 | 221 | -0.45% | 6 | 37 | Township |
| Geneva | 15 | 141 | 136 | 1.44% | 5 | 30 | Township |
| Deer Creek | 16 | 105 | 105 | -0.94% | 3 | 36 | Township |
| Savonburg | 17 | 76 | 75 | 0% | 396 | 0 | City |
| Earlton | 18 | 57 | 59 | -1.72% | 356 | 0 | City |
| Elsmore | 19 | 51 | 53 | -1.92% | 336 | 0 | City |
| Urbana | 20 | 25 | 24 | 8.7% | 15 | 2 | CDP |
| Bassett | 21 | 22 | 22 | 0% | 328 | 0 | City |
| Lone Elm | 22 | 22 | 22 | 0% | 324 | 0 | City |
| Mildred | 23 | 15 | 23 | 7.14% | 22 | 1 | CDP |
Iola is the largest city in Allen County, with a population of 5,286.
Mildred is the smallest city in Allen County, with a population of 15.
There are 23 cities in Allen County, Kansas.