| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density (/mi²) | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Onawa | 1 | 2,797 | 2,907 | -0.85% | 531 | 5 | City |
| Mapleton | 2 | 1,126 | 1,159 | -0.79% | 716 | 2 | City |
| Whiting | 3 | 733 | 748 | -0.68% | 721 | 1 | City |
| Ute | 4 | 325 | 341 | -1.22% | 874 | 0 | City |
| Blencoe | 5 | 224 | 232 | -0.88% | 295 | 1 | City |
| Moorhead | 6 | 187 | 198 | -1.58% | 796 | 0 | City |
| Soldier | 7 | 177 | 183 | -1.12% | 571 | 0 | City |
| Castana | 8 | 102 | 105 | -0.97% | 112 | 1 | City |
| Turin | 9 | 68 | 71 | -1.45% | 756 | 0 | City |
| Rodney | 10 | 42 | 45 | -2.33% | 276 | 0 | City |
Onawa is the largest city in Monona County, with a population of 2,797.
Rodney is the smallest city in Monona County, with a population of 42.
There are 10 cities in Monona County, Iowa.