Maine - Area of significance: Architecture
| Peters, John, House |
| Petit Manan Light Station |
| Pettegrove, Joshua, House |
| Pettengill House and Farm |
| Phi Gamma Delta House |
| Philbrook, John M., House |
| Philbrook, Samuel D., House |
| Philler Cottage |
| Phillips High School |
| Pilley House |
| Pilsbury Block |
| Pittsfield Public Library |
| Pittsfield Railroad Station |
| Pittsfield Universalist Church |
| Pittston Congregational Church |
| Pittston Farm |
| Pleasant River Grange No. 492 |
| Plummer, Capt. John, House |
| Poland Railroad Station |
| Poland Spring Beach House, (Former) |
| Poland Spring Bottling Plant and Spring House |
| Porteous, Mitchell and Braun Company Building |
| Porter-Bell-Brackley Estate |
| Porter Memorial Library |
| Porter Old Meetinghouse |
| Portland Breakwater Light |
| Portland City Hall |
| Portland City Hospital |
| Portland Club |
| Portland Headlight |
| Portland High School |
| Portland Observatory |
| Portland Packing Company Factory |
| Portland Soldiers and Sailors Monument |
| Portland Waterfront |
| Portsmouth Company Cotton Mills: Counting House |
| Portsmouth Naval Shipyard |
| Pote, Capt. Greenfield, House |
| Powers House |
| Powers, Peter, House |
| Prescott, J. L., House |
| Presque Isle National Bank |
| Pressey House |
| Primrose Hill Historic District |
| Prince, Cushing and Hannah, House |
| Professional Building |
| Proprietors Meeting House and Parish House |
| Prospect Harbor Light Station |
| Prouty, Jed, Tavern and Inn |
| Pumpkin Island Light Station |
| Purington, Elisha, House |
| Putnam, Blackhawk, Tavern |
| Pythian Opera House |
| Quimby, Dr. Samuel, House |
| Quincy Building |
| Rackleff Building |
| Ram Island Light Station |
| Ramsdell, Hiram, House |
| Randall-Hildreth House |
| Randall, Jacob, House |
| Rangeley Trust Company Building |
| Rankin Block |
| Raventhorp |
| Readfield Union Meeting House |
| Record, E.C. and M.I., Homestead |
| Record, Judson, House |
| Redington House |
| Redwood |
| Reed, Philo, House |
| Reed, Robert, House |
| Reverie Cove |
| Rice Public Library |
| Richardson House |
| Richmond Historic District |
| Riggs, Benjamin, House |
| Rivercroft Farm |
| River Meetinghouse |
| Riverview House |
| Roak Block |
| Robinhood Free Meetinghouse |
| Robinson-Parsons Farm |
| Robinson, William A., House |
| Rockland Breakwater Lighthouse |
| Rockland Public Library |
| Rockland Railroad Station |
| Rockland Residential Historic District |
| Rockport Historic District |
| Roosevelt School |
| Roosevelt School |
| Ropes End |
| Rose, Robert, Tavern |
| Row House |
| Ruggles House |
| Rumford Commercial Historic District |
| Rumford Falls Paper Company Historic District |
| Rumford Falls Power Company Building |
| Rumford Public Library |
| Saco City Hall |
| Saco High School (old) |
| Saco Historic District |
Data from United States Park Service and Wikidata
