City | 2024 Population |
|---|---|
| Oak Harbor | 23,813 |
| Oakesdale | 392 |
| Oakville | 730 |
| Ocean City | 60 |
| Ocean Park | 1,832 |
| Ocean Shores | 7,808 |
| Ocosta | 79 |
| Odessa | 936 |
| Okanogan | 2,434 |
| Olympia | 55,774 |
| Omak | 5,051 |
| Onalaska | 701 |
| Orchards | 30,900 |
| Orient | 12 |
| Oroville | 1,866 |
| Orting | 8,923 |
| Oso | 385 |
| Othello | 8,985 |
| Otis Orchards-East Farms | 5,430 |
| Outlook | 384 |
| Oyehut | 102 |