Maryland - Area of significance: Architecture
| McCauley, Henry, Farm |
| McDonogh Place Historic District |
| McKim's School |
| McKinstry's Mills Historic District |
| McMurray-Frizzell-Aldridge Farm |
| McPherson's Purchase |
| Meadow Brook Farm |
| Medicine Hill |
| Melford |
| Melwood Park |
| Memory Lane |
| Mercantile Deposit and Trust |
| Mercantile Trust and Deposit Company |
| Mercy Chapel at Mill Run |
| Merry Sherwood |
| Mesrobian, Mihran, House |
| Middle, East and West Halls |
| Middleham Chapel |
| Middletown Historic District |
| Midtown Edmondson Historic District |
| Milimar |
| Miller, H.F. Miller & Son Tin Box and Can Manufacturing Plant |
| Miller's House |
| Mill Green Historic District |
| Mitchell House |
| Mitchell House |
| Montgomery County Courthouse Historic District |
| Montgomery Ward Warehouse and Retail Store |
| Montpelier |
| Montrose |
| Montrose Mansion and Chapel |
| Montrose Schoolhouse |
| Moreland |
| Morgan Hill Farm |
| Morgan Park Historic District |
| Morgan State University Memorial Chapel |
| Mother Seton House |
| Motter, John C., House |
| Mountain Lake Park Historic District |
| Mount Air |
| Mount Airy |
| Mount Airy |
| Mount Airy Historic District |
| Mount Aventine |
| Mount Clare |
| Mount de Sales Academy |
| Mount Lubentia |
| Mount Pleasant |
| Mount Rainier Historic District |
| Mount Royal Station |
| Mount Vernon Mill No. 1 |
| Mount Vernon Place Historic District |
| Mount Vernon Place United Methodist Church and Asbury House |
| Moyaone Reserve Historic District |
| 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 |
| My Lady's Manor |
| Myrtle Grove |
| Nallin Farm House |
| Nallin Farm Springhouse and Bank Barn |
| Nanticoke Lodge No. 172, A.F. and A.M. |
| National Park Seminary Historic District |
| Naval Ordnance Laboratory |
| NELLIE CROCKETT |
| Nelson, Henry, House |
| Nelson Homestead |
| Nelson-Reardon-Kennard House |
| New Mark Commons |
| New Market Historic District |
| New Windsor Historic District |
| Nicodemus Mill Complex |
| NIST Historic District |
| Norman's Retreat |
| Norris-Stirling House |
| North Brentwood Historic District |
| North Central Historic District |
| Northern District Police Station |
| Northwood Historic District |
| Null House |
| Nun's Green |
| Oakdale |
| Oakenshawe Historic District |
| Oak Grove |
| Oak Hill Historic District |
| Oakland |
| Oakland |
| Oakland Historic District |
| Oakland Mills Blacksmith House and Shop |
| Oak Lawn |
| Oaks II |
| Oakwood |
| Obligation |
| Ocean Hall |
| Octorara Farm |
Data from United States Park Service and Wikidata
