All - Constructed - 1910–1919
| Oneida County Courthouse |
| Oneida Milling and Elevator Company Grain Elevator |
| Onion Creek Bridge |
| Oppenheimer House |
| Orchestra Hall |
| Oregon State Hospital Historic District |
| Orpheum Theatre |
| Orpheum Theatre |
| Orville Beach Memorial Manual Training School |
| Osage City Santa Fe Depot |
| Osborne Public Carnegie Library |
| Osgood Bradley Building |
| Oskaloosa Monthly Meeting of Friends Parsonage |
| Osseo Water Tower |
| Oswego Public Carnegie Library |
| Oteen Veterans Administration Hospital Historic District |
| Ottawa High School and Junior High School |
| Our Lady of Good Voyage Church |
| Our Lady of Limerick Catholic Church |
| Our Lady of the Blessed Sacrament Church |
| Our Lady of the Wayside |
| Overbrook |
| Overlook |
| Owl's Nest Country Place |
| Oxley Barn |
| Pacific County Courthouse |
| Pacific Electric Railroad Bridge |
| Paine Furniture Building |
| Palace Hotel |
| Palace of Fine Arts |
| Palace Theater |
| Palace Theater |
| Palmer, O. K., House |
| Palmetto Building |
| Palo, John and Justina, Homestead |
| Panama Hotel |
| Pan American Union |
| Pantego Academy |
| Paradise Inn |
| Parker Jail |
| Parker, John, House |
| Parks, Rosa L. (McCauley) and Raymond, Flat |
| Park View School |
| Parsons Memorial Lodge |
| Passionist Fathers Monastery |
| Pastorium, Dexter Avenue Baptist Church |
| Patterson Hotel |
| Paul, Denton J., Water Tank |
| Payette City Hall and Courthouse |
| Payette Lakes Club |
| Peabody Museum of Salem |
| Peabody Township Carnegie Library |
| Peachtree Southern Railway Station |
| Peck, George B., Dry Goods Company Building |
| Peltier House |
| Penn Central Station |
| Pennington, S. A., House |
| Pennsylvania Station |
| People's Federal Savings and Loan Association |
| Peoples Gas Building |
| People's National Bank Building |
| Peoples National Bank Building |
| Perkins, Arthur, House |
| Perkins, Frances, House |
| Perkins, George and Lola, House |
| Philipse Manor Railroad Station |
| Phillips School |
| Physical Education Building/La Crosse State Normal School |
| Piedmont Park Apartments |
| Pierce, Elijah, Properties |
| Pierce, F. Lincoln, Houses |
| Pigford Building |
| Pinewoods Camp |
| Pioneer School House |
| Pittock Mansion |
| Pittsburgh and Lake Erie Passenger Station, Aliquippa |
| Pittsburg Public Library |
| Plana School |
| Plant City High School |
| Plays and Players |
| Pleasant View School |
| Plymouth Building |
| Plymouth Congregational Church |
| Poke-O-Moonshine Mountain Fire Observation Station |
| Polish National Home |
| Polson Feed Mill |
| Polson, Mrs. Richard, House |
| Ponce Public School 1913 |
| Pontiac Hotel |
| Poole, Wayland E., House |
| Popular Department Store |
| Porter-Crawford House |
| Porter, Nathan T. and Anna, House |
| Porterville General Store |
| Portland Fire Station No. 17 |
| Potter County Courthouse |
| Poughkeepsie Railroad Station |
| Pousette-Dart, Richard, House and Studio |
| Powell Bridge |
| Pratt School |
Data from United States Park Service and Wikidata
