California - Criteria: A (event)
| Napa Valley Railroad Depot |
| National Bank of San Mateo |
| National Bank of Whittier Building |
| National Exchange Hotel |
| National Farm Workers Association Headquarters |
| 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 |
| Nevada Brewery |
| Nevada City Downtown Historic District |
| Nevada City Free Public Library |
| Nevada Theatre |
| New Almaden |
| Newcastle Portuguese Hall |
| New Hotel Carquinez |
| Newland House |
| NIANTIC (Storeship) |
| Nichelini Winery |
| Nicholson, Grace, Building |
| Niles Canyon Transcontinental Railroad Historic District |
| Nippon Hospital |
| Nobles Emigrant Trail |
| North Hollywood Branch |
| North Star House |
| Nuestra Senora Reina de la Paz |
| Nystrom Elementary School-The Maritime Building |
| Oak Grove Butterfield Stage Station |
| 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 |
| Oaks, The |
| Oakville Grocery |
| Oddfellows Hall |
| Odd Fellows Hall |
| Odd Fellows Hall |
| Odd Fellows Hall |
| O'Donnell, Thomas, House |
| Offerman, John, House |
| Ohm, John, House |
| Old Administration Building, Fresno City College |
| Old Adobe Barn |
| Old Auburn Historic District |
| Old Bank of America Building |
| Old Borges Ranch |
| Old City Hall |
| Old City Hall Building |
| Old Fresno Water Tower |
| Old La Grange Schoolhouse |
| Old Masonic Hall |
| Old Mission Dam |
| Old Napa Register Building |
| Old Pasadena Historic District |
| Old Point Loma Lighthouse |
| Old Sacramento 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 Town San Diego Historic District |
| Old U.S. Mint |
| Old Weber School |
| Old YWCA Building |
| Olema Lime Kilns |
| Olema Valley Dairy Ranches Historic District |
| Olinsky Building |
| Olivas Adobe |
| Olive Civic Center |
| Olivenhain Town Meeting Hall |
| Ontario and San Antonio Heights Waiting Station |
| Ontario State Bank Block |
| Orange County Courthouse |
| Orange Cove Santa Fe Railway Depot |
| Oregon Creek Covered Bridge |
| Orosi Branch Library |
| Oroville Chinese Temple |
| Oroville Inn |
| Ostrander Lake Ski Hut |
| Osuna, Juan Maria, Adobe |
| Otis Elevator Company Building |
| Ott's Assay Office |
| Our Lady of the Wayside |
| Outdoor Art Club |
| Oviatt, James, Building |
| Oxnard, Henry T., Historic District |
| Oxnard Public Library |
| Pacific Biological Laboratories |
| Pacific Coast Railway Company Grain Warehouse |
| Pacific Electric Building |
| Pacific Electric Etiwanda Depot |
| Pacific Electric Railway Company Depot |
Data from United States Park Service and Wikidata
