All - Architectural style - Georgian architecture
| Lewden, John, House |
| Lincoln, Asa, House |
| Lincoln, Mary Todd, House |
| Liriodendron |
| Lloyd House |
| Longfellow House-Washington’s Headquarters National Historic Site |
| Loockerman Hall |
| Lowndes Grove |
| Lukens Main Office Building |
| MacPheadris-Warner House |
| Main Street School |
| Mankin Mansion |
| Mann, Andrew, Inn |
| Mannington Historic District |
| Maple Grove Farm |
| Marlbrook |
| Marshall, Humphry, House |
| Marshall, Thomas, House |
| Marshfield Elks Temple |
| Marston, William, House |
| Martin Orthopedic School |
| Maryland Statehouse |
| Marywood Academy |
| Maybury Hill |
| Mayfair Apartments |
| Maynard, Thomas, House |
| McAllister, Archibald, House |
| McCann, Thomas, House |
| McCobb-Hill-Minott House |
| McColley, James, House |
| McConnell House, Law Office, and Slave Quarters |
| McNish, Alexander, House |
| Melwood Park |
| Memorial Continental Hall |
| Memorial Hall |
| Merestead |
| Merrill Estate |
| Mexico Academy and Central School |
| Michigan-Lee Apartments |
| Middleport Public Library |
| Milimar |
| Miller, Johannes, House |
| Mill House |
| Mills, Lewis H., House |
| Milton |
| Mission House |
| Mitchell House |
| Moffatt-Ladd House |
| Monterey |
| Monterey Historic District |
| Montgomery, John Rogerson, House |
| Montgomery Ward Building |
| Montpelier |
| Monument Avenue Historic District |
| Mooney, Edward, House |
| Moore, Elizabeth, Hall |
| Morrell House |
| Morse, Daniel, III, House |
| Morse-Tay-Leland-Hawes House |
| Moseley House-Farm |
| Mountain View |
| Mountain View Farm |
| Mount Clare |
| Mount Pleasant |
| Mount Pleasant |
| Mount Pleasant |
| Mount St. Mary's Academy and Convent |
| Mount, The |
| Mount Vernon |
| Mt. Nebo |
| Mulberry Fields |
| Mulliss, George W. F., House |
| Munro-Hawkins House |
| Murphy-Burroughs House |
| Naudain, Arnold S., House |
| Neighborhood House |
| Newcomb-Brown Estate |
| Nichols, Daniel, Homestead |
| Nichols, Jerry, Tavern |
| Nicholson, Abel and Mary, House |
| North Wales |
| Norton, Julius and Sophia, House |
| Nye, Elnathan, House |
| Oakes, Edward, House |
| Oak Hill |
| Old Cann Mansion House |
| Old Christ Church |
| Old Drawyers Church |
| Old Manse |
| Old North Church |
| Old Statehouse |
| Old State House |
| Old Stone Fort |
| Old Stone Tavern |
| Old Sussex County Courthouse |
| Old Town Hall |
| Old Tuscaloosa County Jail |
| Oliver House |
| Olney Elementary School |
| Oregon Electric Railway Passenger Station |
Data from United States Park Service and Wikidata
