All - Architectural style - Romanesque Revival architecture
| Old Main, Macalester College |
| Old Main, Nebraska Wesleyan University |
| Old McCulloch County Jail |
| Old Middletown High School |
| Old Minnehaha County Courthouse |
| Old Post Office |
| Old Post Office and Clock Tower |
| Old Public Library |
| Old School Privy |
| Old South Church |
| Old Springdale High School |
| Old St. Johns County Jail |
| Old St. Mary's Church |
| Old Stone Church |
| Old Union Depot |
| Old Victoria County Courthouse |
| Old Water and Electric Light Plant |
| Oleson-Crane Building |
| Omaha Bolt, Nut and Screw Building |
| Onawa IOOF Opera House |
| Oneida Stake Academy |
| Ontonagon County Courthouse |
| Oquirrh School |
| Orange County Courthouse |
| Orient Manufacturing Company-Chadwick-Hoskins No. 3 |
| Orlando Flats |
| Osage Bank of Fairfax |
| Osborne County Courthouse |
| Osborne School |
| Osborn Street School |
| Oshkosh Grand Opera House |
| Our Lady of Limerick Catholic Church |
| Our Lady of Lourdes Church |
| Our Lady of Mount Carmel Church |
| Our Lady of Peace Cathedral |
| Our Savior's Scandinavian Lutheran Church |
| Overlook |
| Owatonna City and Firemen's Hall |
| Pacific Coast Biscuit Company Building |
| Pacific Electric Building |
| Palace Hotel |
| Palmer Hall |
| Palmer Memorial Hall |
| Palmyra Methodist Episcopal Church |
| Panola County Jail |
| Parberry Block East |
| Parke-Davis and Company Pharmaceutical Company Plant |
| Parke-Davis Research Laboratory |
| Parker Building |
| Parkhurst Memorial Presbyterian Church |
| Park Region Luther College |
| Park Street Railroad Station |
| Parlin Library |
| Parmly Billings Memorial Library |
| Parrott Insurance Building |
| Pawtucket Congregational Church |
| Pawtucket Congregational Church |
| Peabody, Elizabeth, School |
| Peabody School |
| Pearsons Hall of Science |
| Peirce, John, House |
| Pella Opera House |
| Peoria Waterworks |
| Peteetneet School |
| Petersen's, J. H. C., Sons Store |
| Peyser and Morrison Shirt Company Building |
| Phillips High School |
| Phipps-Wallace Store Building |
| Pierce, Carrie, House |
| Piggott, Charles, House |
| Pike County Courthouse |
| Pilgrim Baptist Church |
| Pilgrim Congregational Church |
| Pilgrim Congregational Church |
| Pilgrim Congregational Church |
| Pilgrim Memorial Church and Parish House |
| Pillsbury Academy Campus Historic District |
| Pillsbury Memorial Hall |
| Pilsbury Block |
| Pittsgrove Presbyterian Church |
| Planters National Bank |
| Plumb Memorial Library |
| Plymouth Congregational Church |
| Plymouth Congregational Church |
| Plymouth Theater |
| Pocahontas County Courthouse and Jail |
| Poile Zedek Synagogue |
| Pointe Coupee Parish Courthouse |
| Police Station No. 5 |
| Polk County Courthouse |
| Pontiac City Hall and Fire Station |
| Porter, Dr. D. T., Building |
| Porter Memorial Library |
| Port Gibson United Methodist Church |
| Port Henry Fire Department Building |
| Pottsville Armory |
| Poughkeepsie Meeting House (Montgomery Street) |
| Presbyterian Church Building |
| Preston Castle |
| Primera Iglesia Bautista de Caguas |
Data from United States Park Service and Wikidata
