New York - Significance region: Local
| Old Gravesend Cemetery |
| Old Grolier Club |
| Old Hartwick Village Cemetery |
| Old Homer Village Historic District |
| Old Lowville Cemetery |
| Old Lutheran Parsonage |
| Old Madison County Courthouse |
| Old Nassau County Courthouse |
| Old New York Evening Post Building |
| Old Parsonage |
| Old Post Office |
| Old School Baptist Church of Halcottsville |
| Old Sloatsburg Cemetery |
| Old Southeast Church |
| Old Southeast Town Hall |
| Old State Road Bridge |
| Old Stone Fort |
| Old Stone House Library, The |
| Old Stone House of Brooklyn, The |
| Old Stone Warehouse |
| Old Town Green Historic District |
| Old Town Hall Historic District |
| Old Town of Flushing Burial Ground |
| Old Trees |
| Old Troy Hospital |
| Old Warren County Courthouse Complex |
| Olean Armory |
| Olean Public Library |
| Olean School #10 |
| Olive and Hurley Old School Baptist Church |
| Oliver Avenue Bridge |
| Oliver, Thomas, House |
| Olivet Chapel |
| Olmstead Street Historic District |
| Onderdonk, Horatio Gates, House |
| Onderdonk House |
| Oneida Armory |
| Oneida Community Limited Administration Building |
| Oneida Downtown Commercial Historic District |
| Oneida Lake Congregational Church |
| Oneonta Armory |
| Oneonta Downtown Historic District |
| Oneonta Theatre |
| Onondaga County War Memorial |
| Onondaga Highlands-Swaneola Heights Historic District |
| Onondaga Park |
| Ontario and Livingston Mutual Insurance Office |
| Ontario and Western Railroad Passenger Station |
| Onteora Park Historic District |
| Oran Community Church |
| Oran District No. 22 Schoolhouse |
| Orchard Shoal Light Station, Old |
| Ordway, Jones, House |
| Orient Historic District |
| Orient Point Light Station |
| Orleans County Courthouse Historic District |
| Ormonde |
| Ormsby-Laughlin Textile Companies Mill |
| Osborn-Bouton-Mead House |
| Osborne Apartments |
| Osborne House |
| Osburn, Mrs., House |
| Osceola Town Hall |
| Osgood, J.C., Firehouse |
| Oswegatchie Pumping Station |
| Oswego Armory |
| Oswego City Hall |
| Oswego County Courthouse |
| Oswego Meeting House and Friends' Cemetery |
| Oswego-Oneida Streets Historic District |
| Oswego Theater |
| Oswego Yacht Club |
| Otis, Job and Deborah, House |
| Otsdawa Baptist Church |
| Otter Lake Community Church |
| Ouaquaga Lenticular Truss Bridge |
| Oulagisket |
| Our Lady of Mount Carmel Grotto |
| Our Lady of Victory National Shrine and Basilica Historic District |
| Our Lady of Victory Roman Catholic Church |
| Our Mother of Good Counsel Roman Catholic Church Complex |
| Our Mother of Sorrows Roman Catholic Church Complex |
| Oval Wood Dish Factory |
| Overackers Corners Schoolhouse |
| Overlook |
| Owasco Reformed Church |
| Owego Central Historic District |
| O & W Railroad Station at Port Ben |
| Oxford Village Historic District |
| Oyster Bay Long Island Rail Road Station |
| Oyster Bay Long Island Rail Road Turntable |
| Packard Motor Car Showroom and Storage Facility |
| Packer Farm and Barkersville Store |
| Paddock Building |
| Paddock Mansion |
| Paddy’s Market Historic District |
| PAD Factory, The |
| Pagan-Fletcher House |
| Page House |
| Pakatakan Artists Colony Historic District |
Data from United States Park Service and Wikidata
