California - Significance region: Local
| Old Farmdale School |
| Old Fresno Water Tower |
| Old Jacoby Creek School |
| Old La Grange Schoolhouse |
| Old Masonic Hall |
| Old Napa Register Building |
| Old Ohio Street Houses |
| Old Pasadena Historic District |
| Old Petaluma Opera House |
| Old Point Loma Lighthouse |
| Old Post Office |
| Old Riverview Historic District |
| Old San Antonio Hospital |
| Old Santa Rosa Catholic Church and Cemetery |
| Old Santa Susana Stage Road |
| Old Tavern |
| Old Towne Orange Historic District |
| Old Weber School |
| Old YWCA Building |
| Olema Valley Dairy Ranches Historic District |
| Olinsky Building |
| Olive Civic Center |
| Olivenhain Town Meeting Hall |
| Olsen, Donald and Helen, House |
| Olvida Penas |
| O'Men Village Site |
| One Lombard Street |
| Ontario and San Antonio Heights Waiting Station |
| Ontario Baseball Park |
| Orange Cove Santa Fe Railway Depot |
| Orange Grove Court |
| Orange Intermediate School-Central Grammar School |
| Orange Lawn |
| Orange Union High School |
| Orosi Branch Library |
| Oroville Carnegie Library |
| Oroville Commercial District (old) |
| Oroville Inn |
| Ostrander Lake Ski Hut |
| Osuna, Juan Maria, Adobe |
| Otis Elevator Company Building |
| Outdoor Art Club |
| Outlands in the Eighty Acres |
| Oviatt, James, Building |
| Oxnard, Henry T., Historic District |
| Oxnard Public Library |
| OX Ranch Headquarters |
| Pacheco, Don Fernando, Adobe |
| Pacific Coast Railway Company Grain Warehouse |
| Pacific Electric Building |
| Pacific Electric Etiwanda Depot |
| Pacific Electric Railroad Bridge |
| Pacific Electric Railway Company Depot |
| Pacific Electric Railway Company Substation No. 8 |
| Pacific Electric Sub-Station No. 14 |
| Pacific Gas and Electric Company Substation J |
| Pacific Gas & Electric Company Building |
| Pacific Press Building |
| Packard Library |
| Paddison Ranch Buildings |
| Padua Hills Theatre |
| Paige Motor Car Co. Building |
| Palace Hotel |
| Palace of Fine Arts |
| Palmer, Annie, House |
| Palmer, Judge Augustus C., House |
| Palmer, Minnie Hill, House |
| Palmetto Court |
| Palm Springs Aerial Tramway Mountain Station |
| Palm Springs City Hall |
| Palm Springs Desert Museum |
| Palm Springs Municipal Airport Terminal |
| Palm Springs Tramway Valley Station |
| Palm Springs Unified School District Educational Administrative Center |
| Palo Alto Medical Clinic |
| Palo Alto Southern Pacific Railroad Depot |
| Palomares, Ygnacio, Adobe |
| Palos Verdes Public Library and Art Gallery |
| Panama Hotel |
| Panoramic Hill |
| Pantages, Alexander, Theater |
| Park Apartments |
| Parker House |
| Park Headquarters, Lassen Volcanic National Park |
| Parkhurst Building |
| Park Place Methodist Episcopal Church South |
| Park Street Historic Commercial District |
| Park View Hotel |
| Parmelee, Lou Ellen, House |
| Parra, Miguel, Adobe |
| Pasadena Arroyo Parks and Recreation District |
| Pasadena Avenue Historic District |
| Pasadena Field Archery Range |
| Pasadena Playhouse Historic District |
| Paso Robles Almond Growers Association Warehouse |
| Patio del Moro |
| Patrick Ranch House |
| Patterson Branch Library |
| Patterson, George Washington, Ranch-Ardenwood |
| Patwin Indian Site |
Data from United States Park Service and Wikidata
