Louisiana - Area of significance: Architecture
| Nottoway Plantation House |
| Oak Alley Plantation |
| Oak Grove Community House |
| Oak Grove Plantation Dependencies |
| Oak Hall |
| Oakland Cemetery |
| Oakland Plantation House |
| Oaklawn Manor |
| Oaklawn Plantation |
| Oakley Plantation House |
| Oaks, The |
| Oaks, The |
| Oakwold Plantation House |
| O'Bier House |
| Odd Fellows Rest Cemetery |
| Oil and Gas Building |
| Oil Center Historic District |
| Oil City School |
| Old Arabi Historic District |
| Old Commercial National Bank Building |
| Old Courthouse Square |
| Old Federal Building |
| Old Guaranty Bank Building |
| Old Handleman Building |
| Old Hickory |
| Old Jefferson Parish Courthouse |
| Old Louisiana Governor's Mansion |
| Old Louisiana State Capitol |
| Old Meat Market-Old Meat Market |
| Old Pineville Town Hall |
| Old Post Office |
| Old St. Helena Parish Jail |
| Old Ursuline Convent |
| Olivier Pigeonnier |
| Olivier Store |
| Opelousas City Hall |
| Opelousas Historic District |
| Orange Grove Plantation House |
| Ormond Plantation House |
| Orpheum Theatre |
| Ory House |
| Ouachita Parish High School |
| Our Lady of Peace Catholic Church |
| Palace Theatre |
| Palo Alto Dependency |
| Palo Alto Plantation |
| Pan-American Life Insurance Company Building |
| Park View Guest House |
| Parkview Historic District |
| Parlange Plantation House |
| Pascal Building |
| Patin House |
| Pecan Grove Plantation House |
| Pecue House |
| Pegram Plantation House |
| Pellerin-Chauffe House |
| Peltier House |
| Penne, Henri, House |
| Pennington, S. A., House |
| People's National Bank |
| Percy-Lobdell Building |
| Perry House |
| Pessou House |
| Petitpierre-Kleinpeter, Joseph, House |
| Petroleum Tower |
| Pitot House |
| Plaquemine High School |
| Plaquemine Historic District |
| Pleasant View Plantation House |
| Poche House |
| Poche', Judge Felix, Plantation House |
| Pointe Coupee Parish Courthouse |
| Pointe Coupee Parish Museum |
| Poiret Place |
| Ponchatoula Commercial Historic District |
| Pontalba Buildings |
| Poplar Chapel AME Church |
| Poplar Grove Plantation House |
| Port Allen High School |
| Port Hudson National Cemetery |
| Potts House |
| Poydras High School |
| Presbytere, The |
| Prescott Memorial Library-Louisiana Tech University |
| President's Home, Northwestern State University |
| Prude House |
| Prud'homme, Jean Pierre Emmanuel, Oakland Plantation |
| Prudhomme, Michel, House |
| Rabalais House |
| Rabassa, Jean Louis, House |
| Randal House |
| Rankin House |
| Ransonet House |
| Rapides Bank and Trust Company Building |
| Rapides Opera House |
| Rapides Parish Library |
| Rawls Cabin |
| Ray Homestead |
| Rayville High School |
| Raziano House |
Data from United States Park Service and Wikidata
