32 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| St. James | 1 | 4,737 | 4,809 | -0.27% | 2,030 | 2 | City |
| St. James | 2 | 4,737 | 4,802 | -0.27% | 2,030 | 2 | City |
| Madelia | 3 | 2,438 | 2,400 | 0.33% | 1,612 | 2 | City |
| Madelia | 4 | 2,438 | 2,397 | 0.33% | 1,612 | 2 | City |
| Butterfield | 5 | 596 | 601 | -0.17% | 1,472 | 0 | City |
| Butterfield | 6 | 596 | 600 | -0.17% | 1,472 | 0 | City |
| Madelia | 7 | 302 | 304 | 0% | 9 | 33 | Township |
| Madelia | 8 | 302 | 303 | 0% | 9 | 33 | Township |
| Riverdale | 9 | 285 | 285 | 0% | 7 | 39 | Township |
| Riverdale | 10 | 285 | 284 | 0% | 7 | 39 | Township |
| Rosendale | 11 | 270 | 272 | 0% | 7 | 38 | Township |
| Rosendale | 12 | 270 | 271 | 0% | 7 | 38 | Township |
| Antrim | 13 | 265 | 267 | 0% | 7 | 36 | Township |
| Antrim | 14 | 265 | 266 | 0% | 7 | 36 | Township |
| South Branch | 15 | 252 | 254 | 0% | 6 | 39 | Township |
| South Branch | 16 | 252 | 254 | 0% | 6 | 39 | Township |
| St. James | 17 | 226 | 228 | 0% | 7 | 34 | Township |
| St. James | 18 | 226 | 228 | 0% | 7 | 34 | Township |
| Lewisville | 19 | 207 | 206 | 0% | 845 | 0 | City |
| Lewisville | 20 | 207 | 206 | 0% | 845 | 0 | City |
| Fieldon | 21 | 205 | 206 | 0% | 6 | 36 | Township |
| Fieldon | 22 | 205 | 206 | 0% | 6 | 36 | Township |
| Butterfield | 23 | 198 | 199 | 0% | 6 | 35 | Township |
| Butterfield | 24 | 198 | 199 | 0% | 6 | 35 | Township |
| Odin | 25 | 161 | 164 | -1.23% | 5 | 35 | Township |
| Odin | 26 | 161 | 164 | -1.23% | 5 | 35 | Township |
| Odin | 27 | 123 | 125 | -0.81% | 332 | 0 | City |
| Odin | 28 | 123 | 125 | -0.81% | 332 | 0 | City |
| Darfur | 29 | 82 | 84 | -1.2% | 358 | 0 | City |
| Darfur | 30 | 82 | 84 | -1.2% | 358 | 0 | City |
| La Salle | 31 | 75 | 75 | 0% | 862 | 0 | City |
| La Salle | 32 | 75 | 75 | 0% | 862 | 0 | City |
St. James is the largest city in Watonwan County, with a population of 4,737.
La Salle is the smallest city in Watonwan County, with a population of 75.
There are 32 cities in Watonwan County, Minnesota.