California - Criteria: C (architecture/engineering)
| National Exchange Hotel |
| Natural History Museum |
| Naval Air Station Alameda Historic District |
| Naval Air Station, San Diego, Historic District |
| Naval Training Station |
| Navarro |
| NCO Railway Depot |
| Nesbitt, Sheriff William Joseph, House |
| Neutra Office Building |
| Neutra, Richard and Dion, VDL Research House II |
| Nevada Brewery |
| Nevada-California-Oregon Railway Co. General Office Building |
| Nevada City Downtown Historic District |
| Nevada City Firehouse No. 2 |
| Nevada City Free Public Library |
| Nevada Theatre |
| Newcomb House |
| Newhall Estate |
| New Hotel Carquinez |
| Newland House |
| New Mission Theater |
| New Sequoia Theater Building |
| Nichelini Winery |
| Nicholson, Grace, Building |
| Niles Canyon Transcontinental Railroad Historic District |
| Norris House |
| North Gate Hall |
| North Hollywood Branch |
| North Shore Yacht Club |
| North Star House |
| North University Park Historic District |
| Norton, John, House |
| Noyes Mansion |
| Oakland City Hall |
| Oakland Free Library-Alden Branch |
| Oakland Free Library-Golden Gate Branch |
| Oakland Free Library-Melrose Branch |
| Oakland Hotel |
| Oakland Iron Works-United Works, and the Remillard Brick Company |
| Oakland Lamp Works |
| Oakland Public Library |
| Oakland YWCA Building |
| Oaklawn Bridge and Waiting Station |
| Oaks, The |
| Oceanside City Hall and Fire Station |
| Octagon Building |
| Odd Fellows Building |
| Odd Fellows Hall |
| Odd Fellows Hall |
| Odd Fellows Hall |
| Odd Fellows Temple |
| Offerman, John, House |
| Ohlandt Newlyweds House |
| Ohm, John, House |
| Old Administration Building, Fresno City College |
| Old Adobe Barn |
| Old Auburn Historic District |
| Old Bank of America Building |
| Old City Hall |
| Old City Hall Building |
| Old Fresno Water Tower |
| Old Jacoby Creek School |
| Old La Grange Schoolhouse |
| Old Mission Dam |
| Old Napa Register Building |
| Old Ohio Street Houses |
| Old Pasadena Historic District |
| Old Petaluma Opera House |
| Old Point Loma Lighthouse |
| Old Post Office |
| Old San Antonio Hospital |
| Old Santa Rosa Catholic Church and Cemetery |
| Old Tavern |
| Old Towne Orange Historic District |
| Old U.S. Mint |
| Old Weber School |
| Old YWCA Building |
| Olema Valley Dairy Ranches Historic District |
| Olivas Adobe |
| Olive Civic Center |
| Olsen, Donald and Helen, House |
| Olvida Penas |
| One Lombard Street |
| Ontario State Bank Block |
| Orange County Courthouse |
| Orange Grove Court |
| Orange Lawn |
| Oroville Chinese Temple |
| Oroville Inn |
| Ostrander Lake Ski Hut |
| Osuna, Juan Maria, Adobe |
| Our Lady of the Wayside |
| Outdoor Art Club |
| Outlands in the Eighty Acres |
| Oviatt, James, Building |
| Oxnard, Henry T., Historic District |
| Oxnard Public Library |
| Pacheco, Don Fernando, Adobe |
| Pacific Coast Railway Company Grain Warehouse |
| Pacific Electric Etiwanda Depot |
Data from United States Park Service and Wikidata
