City | 2024 Population |
|---|---|
| Oak Creek | 27 |
| Oak Valley | 55 |
| Oakes | 1,756 |
| Oakhill | 40 |
| Oakland | 27 |
| Oakville | 178 |
| Oakwood | 193 |
| Oberon | 92 |
| Odessa | 11 |
| Odin | 49 |
| Oliver | 28 |
| Olivia | 34 |
| Olson | 22 |
| Ontario | 72 |
| Ops | 38 |
| Ora | 45 |
| Orange | 13 |
| Oriska | 107 |
| Orlien | 44 |
| Orthell | 19 |
| Osago | 39 |
| Osborn | 308 |
| Osford | 39 |
| Oshkosh | 51 |
| Osloe | 37 |
| Osnabrock | 102 |
| Ostby | 51 |
| Otis | 36 |
| Overland | 13 |
| Overly | 10 |
| Ovid | 37 |
| Owego | 30 |
| Oxbow | 369 |