- Olds
- Ocean View Mobile Home Park
- Old Royal
- Old Town
- Ovington
- Ozette Island
- Oak Point
- Olequa
- Oak Park
- Officers Row
- Orondo
- Osborne Corner
- Odair
- Osborne
- Oak Acres Mobile Home Park
- Ocean Grove
- Ocosta
- Onslow
- Oyehut
- Oyehut-Hogans Corner
- Oak Hollow Mobile Home Park
- Olympic View Mobile Home Park
- Oil City
- One Hawkeye Mobile Home Park
- O'Brien
- Ohlers Island
- Orchard Grove
- Orchard Trailer Park
- Orillia
- Osceola