Maryland - Role: Building
| McPherson's Purchase |
| Meadow Brook Farm |
| Meadows, The |
| Medicine Hill |
| Melford |
| Melwood Park |
| Memory Lane |
| Mencken, H. L., House |
| Mercantile Deposit and Trust |
| Mercantile Trust and Deposit Company |
| Mercy Chapel at Mill Run |
| Merry Sherwood |
| Mesrobian, Mihran, House |
| Mettam Memorial Baptist Church |
| Middle, East and West Halls |
| Middleham Chapel |
| Milimar |
| Miller, H.F. Miller & Son Tin Box and Can Manufacturing Plant |
| Miller's House |
| Milton |
| Mitchell, Congressman Parren J., House |
| Mitchell House |
| Mitchell House |
| Montgomery Ward Warehouse and Retail Store |
| Montpelier |
| Montrose |
| Montrose Mansion and Chapel |
| Montrose Schoolhouse |
| Moreland |
| Morgan Hill Farm |
| Morgan State University Memorial Chapel |
| Mother Seton House |
| Motter, John C., House |
| Mount Adams |
| Mount Air |
| Mount Airy |
| Mount Airy |
| Mount Clare |
| Mount de Sales Academy |
| Mount Hope |
| Mount Lubentia |
| Mount Pleasant |
| Mount Vernon Mill No. 1 |
| Mount Vernon Place United Methodist Church and Asbury House |
| Mount Washington Mill |
| Mt. Carmel Monastery |
| Mt. Gilboa Chapel |
| Mt. Moriah African Methodist Episcopal Church |
| Mt. Nebo |
| Mt. Pleasant |
| Mt. Tabor Good Samaritan Lodge #59 |
| Mt. Tabor Methodist Episcopal Church |
| Mt. Zion Memorial Church |
| Mulberry Fields |
| Myrtle Grove |
| Nallin Farm House |
| Nallin Farm Springhouse and Bank Barn |
| Nanticoke Lodge No. 172, A.F. and A.M. |
| National Brewing Company |
| National Enameling and Stamping Company |
| Neck Meetinghouse and Yard |
| Nelson, Henry, House |
| Nelson Homestead |
| Nelson-Reardon-Kennard House |
| New Town Center |
| Nicodemus Mill Complex |
| Norman's Retreat |
| Norris-Stirling House |
| Northern District Police Station |
| Null House |
| Nun's Green |
| Oakdale |
| Oak Grove |
| Oakland |
| Oakland |
| Oakland Mills Blacksmith House and Shop |
| Oak Lawn |
| Oakley, Annie, House |
| Oaks II |
| Oak Street Garage |
| Oakwood |
| Obligation |
| Ocean Hall |
| Octorara Farm |
| Odd Fellows Hall |
| Odd Fellows Lodge |
| O'Dea House |
| Odenton Masonic Lodge No. 209 |
| Old Bloomfield |
| Old Catonsville High School |
| Old Chiswell Place |
| Old City Hall and Engine House |
| Old Forge Farm |
| Old Goucher College Buildings |
| Old Hamilton Library |
| Old Inn, The |
| Old Lock Pump House, Chesapeake and Delaware Canal |
| Old Pine Street Station |
| Old Roman Catholic Cathedral |
| Old Salem Church and Cemetery |
Data from United States Park Service and Wikidata
