23 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Iola | 1 | 5,264 | 5,398 | -0.51% | 1,179 | 4.46 | City |
| Humboldt | 2 | 1,796 | 1,846 | -0.55% | 1,176 | 1.53 | City |
| Elm township | 3 | 1,165 | 1,181 | -0.43% | 25 | 47.15 | Township |
| Iola township | 4 | 768 | 782 | -0.52% | 18 | 42.78 | Township |
| Marmaton township | 5 | 746 | 753 | -0.4% | 13 | 55.55 | Township |
| La Harpe | 6 | 490 | 485 | 0.2% | 615 | 0.80 | City |
| Moran | 7 | 463 | 467 | -0.22% | 1,105 | 0.42 | City |
| Gas | 8 | 462 | 471 | -0.43% | 642 | 0.72 | City |
| Elsmore township | 9 | 351 | 354 | -0.28% | 6 | 63.55 | Township |
| Carlyle township | 10 | 282 | 287 | -0.7% | 9 | 29.75 | Township |
| Humboldt township | 11 | 265 | 270 | -0.75% | 11 | 24.64 | Township |
| Osage township | 12 | 258 | 261 | -0.77% | 5 | 47.88 | Township |
| Salem township | 13 | 242 | 247 | -0.82% | 5 | 47.63 | Township |
| Cottage Grove township | 14 | 218 | 221 | -0.91% | 6 | 36.90 | Township |
| Geneva township | 15 | 140 | 135 | 1.45% | 5 | 29.80 | Township |
| Deer Creek township | 16 | 111 | 106 | 1.83% | 3 | 35.93 | Township |
| Savonburg | 17 | 77 | 76 | 0% | 401 | 0.19 | City |
| Earlton | 18 | 59 | 59 | 0% | 369 | 0.16 | City |
| Elsmore | 19 | 51 | 53 | 0% | 336 | 0.15 | City |
| Urbana | 20 | 25 | 24 | 8.7% | 15 | 1.71 | CDP |
| Bassett | 21 | 22 | 22 | 0% | 328 | 0.07 | City |
| Lone Elm | 22 | 21 | 21 | 0% | 309 | 0.07 | City |
| Mildred | 23 | 15 | 23 | 7.14% | 22 | 0.68 | CDP |
Iola is the largest city in Allen County, with a population of 5,264.
Mildred is the smallest city in Allen County.
There are 23 cities in Allen County, Kansas.