Massachusetts - Criteria: A (event)
| Old Town Bridge |
| Old Town Center Historic District |
| Old Town Farm |
| Old Town Hall |
| Old Town Hall |
| Old Town Hall |
| Old Town Hall Historic District |
| Old Town Historic District |
| Old Town House |
| Old Village Historic District |
| Old Weir Stove Company |
| Oliver House |
| Olmsted-Hixon-Albion Block |
| Olmsted Subdivision Historic District |
| Opposition House |
| Orange Center Historic District |
| Original Congregational Church of Wrentham |
| Orvis Road Historic District |
| Osborn, Benjamin, House |
| Osborn House |
| Osborn Street School |
| Osgood Bradley Building |
| Osgood Hill |
| Osgood, Samuel, House |
| O'Shea Building |
| Osterville Baptist Church |
| Otis Company Mill No. 1 |
| Otis-Wyman House |
| Our Lady Help of Christians Historic District |
| Our Lady of Good Voyage Church |
| Our Mother of Sorrows Monastery and Retreat Center |
| Outing Park Historic District |
| Oxford-Crown Extension District |
| Oxford Main Street Historic District |
| Oxford, The |
| Padanaram Village Historic District |
| Page, Nathaniel, House |
| Paine Estate |
| Paine Furniture Building |
| Paine Hollow Road South Historic District |
| Palmer Island Light Station |
| Palmer Memorial Hall |
| Palmer School |
| Pan Burying Ground |
| Pan Historic District |
| Paragon Park Carousel |
| Park Building |
| Parker-Burnett House |
| Parker, Edmund, Jr., House |
| Parker, James, House |
| Parker Tavern |
| Parker Village Historic District |
| Parkhill Mill |
| Parkman Tavern |
| Park Square Historic District |
| Park Street District |
| Park Street Firehouse |
| Park Street Railroad Station |
| Parsons, Shepherd and Damon, Houses Historic District |
| Patton and Loomis Block |
| Patton Building |
| PAUL PALMER (Shipwreck and Remains) |
| Paul's Bridge |
| Pawtucket Congregational Church |
| Peabody City Hall |
| Peabody Civic Center Historic District |
| Peabody, George, House |
| Peabody Institute |
| Peabody, John P., House |
| Peabody Museum of Salem |
| Peabody, The |
| Peacock Farm Historic District |
| Pearl Street School |
| Peck, John M., House |
| Peirce, Edward, House-Henderson House of Northeastern University |
| Peirce School |
| Pelham Town Hall Historic District |
| Pembroke Friends Meetinghouse |
| Pepperell Center Historic District |
| Pequoig Hotel |
| Perkins Estate |
| Perry Avenue Historic District |
| Pest House |
| Petersham Common Historic District |
| Petterson, Lars-Adolph Carlson Three-Decker |
| Petterson, Lars-Fred Gurney Three-Decker |
| Petterson,Lars-James Reidy Three-Decker |
| Petterson, Lars-Silas Archer Three-Decker |
| Pettibone Farm |
| Phillips, E. M., House |
| Phillipston Center Historic District |
| Phillips Woolen Mill |
| Phinney, William and Jane, House |
| Phipps Street Burying Ground |
| Phoenix Building |
| Piano Row District |
| Pierce, Capt, Mial, Farm |
| Pierce Farm Historic District |
| Pierce, F. Lincoln, Houses |
| Piety Corner Historic District |
Data from United States Park Service and Wikidata
