| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density (/mi²) | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Waukon | 1 | 3,845 | 3,820 | -0.1% | 1,354 | 3 | City |
| Postville | 2 | 2,381 | 2,510 | -0.87% | 1,149 | 2 | City |
| Lansing | 3 | 956 | 961 | -0.1% | 887 | 1 | City |
| New Albin | 4 | 427 | 434 | -0.23% | 1,694 | 0 | City |
| Harpers Ferry | 5 | 277 | 261 | 1.09% | 436 | 1 | City |
| Waterville | 6 | 112 | 108 | 0% | 316 | 0 | City |
Waukon is the largest city in Allamakee County, with a population of 3,845.
Waterville is the smallest city in Allamakee County, with a population of 112.
There are 6 cities in Allamakee County, Iowa.