Maine - Criteria: C (architecture/engineering)
| Lithgow House |
| Lithgow Library |
| Little, Edward, House |
| Littlefield-Chase Farmstead |
| Littlefield-Dustin Farm |
| Littlefield Homestead |
| Littlefield Tavern |
| Little Mark Island Monument |
| Little River Light Station |
| Lockwood Mill Historic District |
| Lombard, Alvin O., House |
| Longfellow, Henry Wadsworth, Monument |
| Long, Zadoc, Free Library |
| Lord Block |
| Lord, Capt. Nathaniel, Mansion |
| Lord-Dane House |
| Lord Farm |
| Lord, James C., House |
| Lord Mansion |
| Loudville Church |
| Lovell Meeting House |
| Lovell Village Church |
| Lower Alewive Historic District |
| Lower Lisbon Street Historic District |
| Lower Meeting House and East Bethel Cemetery |
| Low, Joseph W., House |
| Lubec Channel Light Station |
| Lucerne Inn |
| Ludwig, Godfrey, House |
| Lyceum Hall |
| Machias Post Office and Customhouse |
| Machias Railroad Station |
| Madison Public Library |
| Madrid Village Schoolhouse |
| Maine Central Railroad General Office Building |
| Maine Eye and Ear Infirmary |
| Maine Industrial School for Girls Historic District |
| Maine Publicity Bureau Building |
| Maine State Building |
| Maine State House |
| Maine Supply Company Building |
| Maine Woods Office |
| Main Street-Frye Street Historic District |
| Main Street Historic District |
| Main Street Historic District |
| Mallett, E. B., Office Building |
| Mallett Hall |
| Manana Island Fog Signal Station |
| Manley, Joseph and Susan, Summer Cottage |
| Mann, Arthur L., Memorial Library |
| Manning, Richard, House |
| Manor House |
| Mansion House, The |
| Mansur, Walter P., House |
| Manufacturer's National Bank |
| Maple Grove Friends Church |
| Maplewood Farm |
| Marine Hospital |
| Mariner's Church |
| Market Square Historic District |
| Marrett, Daniel, House |
| Marshall Point Light Station |
| Marsh School |
| Marsh Stream Farm |
| Martel, Dr. Louis J., House |
| Martin, Isaie and Scholastique, House |
| Mason, Dr. Moses, House |
| Masonic Hall |
| Masonic Temple |
| Masonic Temple |
| Matinicus Rock Light Station |
| Maxcy, Joseph and Hannah, Homestead |
| May, Sophie, House |
| McCleary Farm |
| McCobb-Hill-Minott House |
| McCurdy Smokehouse |
| McGilvery, Capt. John, House |
| McGilvery, Capt. William, House |
| McGlashan-Nickerson House |
| McIntire Garrison House |
| McLaughlin House and Garden |
| McLellan House |
| McLellan-Sweat Mansion |
| McWain-Hall House |
| Means, Emily, House |
| Mechanic Institute |
| Mechanics' Hall |
| Memorial Chapel |
| Memorial Hall |
| Mequnticook Golf Club |
| MERCANTILE (schooner) |
| Mercer Union Meetinghouse |
| Merriconegan Farm |
| Merrill, Capt. Reuben, House |
| Merrill, Capt. Reuel and Lucy, House |
| Merrill Hall |
| Merrill-Poor House |
| Merritt, Captain, House |
| Michaud, Fortunat O., House |
| Middle Intervale Meeting House and Common |
Data from United States Park Service and Wikidata
