California Cities
- O'Brien, CA
- O'Neals, CA
- Oak Glen, CA
- Oak Grove, CA
- Oak Hills, CA
- Oak Knoll, CA
- Oak Park, CA
- Oak Run, CA
- Oak Shores, CA
- Oak View, CA
- Oak Village, CA
- Oakdale, CA
- Oakhurst, CA
- Oakland, CA
- Oakley, CA
- Oakville, CA
- Oasis, CA
- Oban, CA
- Obie, CA
- Obregon, CA
- Obrien, CA
- Occidental, CA
- Ocean Roar, CA
- Oceano, CA
- Oceanside, CA
- Ockenden, CA
- Ocotillo, CA
- Ocotillo Wells, CA
- Octol, CA
- Ogilby, CA
- Ohm, CA
- Oil City, CA
- Oildale, CA
- Ojai, CA
- Ojala, CA
- Olancha, CA
- Olcott, CA
- Old Adobe, CA
- Old Bretz Mill, CA
- Old Dale, CA
- Old Fig Garden, CA
- Old Forbestown, CA
- Old Fort Jim, CA
- Old Gilroy, CA
- Old Hilltown, CA
- Old Hopland, CA
- Old Pino, CA
- Old Point Comfort, CA
- Old River, CA
- Old Station, CA
- Old Stine, CA
- Old Town, CA
- Old Town San Diego, CA
- Olde Stockdale, CA
- Oleander, CA
- Olema, CA
- Oleum, CA
- Olga, CA
- Olinda, CA
- Olive Hill, CA
- Olive View, CA
- Olivehurst, CA
- Olivenhain, CA
- Olympia, CA
- Olympic Valley, CA
- Omega, CA
- Omira, CA
- Omo Ranch, CA
- Omus, CA
- One Hundred Palms, CA
- Ono, CA
- Ontario, CA
- Onyx, CA
- Opal Cliffs, CA
- Ophir, CA
- Ora, CA
- Orange, CA
- Orange Blossom, CA
- Orange Cove, CA
- Orange Park Acres, CA
- Orangevale, CA
- Orcutt, CA
- Ordbend, CA
- Ordway, CA
- Oregon City, CA
- Oregon House, CA
- Orford, CA
- Orick, CA
- Orinda, CA
- Orinda Village, CA
- Orita, CA
- Orland, CA
- Orleans, CA
- Orleans Flat, CA
- Ormand, CA
- Oro Fino, CA
- Oro Grande, CA
- Oro Loma, CA
- Oroleve, CA
- Orosi, CA
- Oroville, CA
- Oroville East, CA
- Orris, CA
- Orrs Springs, CA
- Ortega, CA
- Ortonville, CA
- Orwood, CA
- Ostrom, CA
- Oswald, CA
- Oteys Sierra Village, CA
- Otterbein, CA
- Outingdale, CA
- Overlook, CA
- Owenyo, CA
- Owl, CA
- Oxalis, CA
- Oxford, CA
- Oxford Mill, CA
- Oxnard, CA
- Oxnard Beach, CA
- Ozol, CA
