Maine - Role: Building
| Nash, William M., House |
| New Sharon Congregational Church |
| Nichols, Capt. John P., House |
| Nickels-Sortwell House |
| Noble Block |
| Nordica Homestead |
| Norridgewock Female Academy |
| Norridgewock Free Public Library |
| North Berwick Woolen Mill |
| North Jay Grange Store |
| North Monmouth Library |
| North Newport Christian Church |
| North School |
| North Waterford Congregational Church |
| North Yarmouth Academy |
| North Yarmouth and Freeport Baptist Meetinghouse |
| Norton House Historic District |
| Norton's Corner School |
| Norton, William F., House |
| Norumbega |
| Norumbega Carriage House |
| Nutting Homestead, The |
| Oakfield Station |
| Oakland Public Library |
| Oaklands |
| Oak Street School |
| Observer Building |
| Ocean Park Historic Buildings |
| Odd Fellows Block |
| Odd Fellows-Rebekah Hall |
| Ogunquit Memorial Library |
| Ogunquit Playhouse |
| Old Fire Engine House |
| Old Grist Mill |
| Old Hancock County Buildings |
| Old Post Office |
| Old Post Office |
| Old Red Store |
| Old Schoolhouse |
| Old Tavern |
| Old Town House |
| Old Union Meetinghouse |
| Old York Gaol |
| Olmsted, Frederick Law, Summer Home |
| Olsson, Anders and Johanna, Farm |
| Oquossoc Log Church |
| Orgone Energy Observatory |
| Orr's Island Meeting House |
| Osgood Building |
| Osgood Family House |
| Osgood, Nathaniel, House |
| Otisfield Town House (Former) |
| Our Lady of Mount Carmel Catholic Church |
| Owls Head Light Station |
| Paris Public Library |
| Parker House |
| Park Street Row |
| Parson's Bend |
| Parsonsfield Seminary |
| Parsons, Josiah K., Homestead |
| Parsons, Marion, House |
| Parsons-Piper-Lord-Roy Farm |
| Parsons, Stephen, House |
| Patch, Edith Marion, House |
| Patten Building |
| Payson House at Thornhurst |
| Peabody Tavern |
| Peacock Tavern |
| Pebbledene |
| Peck, Bradford, House |
| Pejepscot Paper Company |
| Pemaquid Point Light |
| Pendle Hill |
| Pendleton, James G., House |
| Pennell Institute |
| Penney, Samuel, House |
| Penobscot Salmon Club and Pool |
| Pepperrell, William, House |
| Percy District School House, (Former) |
| Perkins, Charles, House |
| Perkins, John, House |
| Perley, Sam, Farm |
| Perry, Clark, House |
| Perry, William F., House |
| Peters, John, House |
| Pettengill House and Farm |
| Phi Gamma Delta House |
| Philbrook, John M., House |
| Philbrook, Samuel D., House |
| Philler Cottage |
| Phillips High School |
| Pike, LeRoy F., Memorial Building |
| Pilley House |
| Pilsbury Block |
| Pittsfield Public Library |
| Pittsfield Railroad Station |
| Pittsfield Universalist Church |
| Pittston Congregational Church |
| Pleasant River Grange No. 492 |
| Plummer, Capt. John, House |
Data from United States Park Service and Wikidata
