Colorado - Significance region: Local
| Loveland Building and Coors Building |
| Loveland State Amory |
| Luft, Conrad, Sr., House |
| Lulu City Site |
| Lyons Railroad Depot |
| Lyons Sandstone Buildings |
| Macedonia Baptist Church |
| Machebeuf Hall |
| Main Avenue Historic District |
| Main Street Bridge |
| Maitland Arroyo Bridge |
| Maitland Estate |
| Mancos High School |
| Mancos Opera House |
| Manhattan Hotel |
| Manitou Bathhouse |
| Manitou Springs Bridges (2) |
| Manzanola United Methodist Church (MUMC) |
| Marble City State Bank Building |
| Marble High School |
| Marble Jailhouse |
| Marble Town Hall |
| Margery Building |
| Maroon Creek Bridge |
| Martin Mining Complex |
| Masonic Placer Cemetery-Valley Brook Cemetery |
| Masonic Temple Building |
| Mathews House |
| Maxwell Building |
| Maxwell Park School |
| Maxwell, R. G., House |
| Maysville School |
| Maytag Aircraft Building |
| McAllister House |
| McClelland Orphanage |
| McClellan House |
| McClintock Building |
| McClure House |
| McCormick House |
| McCourt, Peter, House |
| McCreery, William H., House |
| McFadden Barn |
| McFadden Brothers Ranch East Headquarters |
| McGraw Ranch |
| McGregor Hall |
| McHugh-Andrews House |
| McIntire Ranch |
| McKenzie Well |
| McPhee and McGinnity Building |
| McPhee and McGinnity Paint Factory |
| Mechanics Building/Masonic Building |
| Meeker Historic District |
| Meeker I.O.O.F. Lodge-Valentine Lodge No. 47 |
| Melvin School |
| Mesa Schoolhouse |
| Methodist Episcopal Church |
| Methodist Episcopal Church of Montrose |
| Metzger Farm |
| Midland Savings Building |
| Midland Terminal Railroad Depot |
| Midland Terminal Railroad Roundhouse |
| Midway House |
| Midwest Steel and Iron Works Company Complex |
| Millage Farm Rural Historic District |
| Mill City House |
| Miller House |
| Milne Farm |
| Milner-Schwarz House |
| Miner Street Bridge |
| Mingus Homestead |
| Minnie Gulch Cabins |
| Mint Saloon |
| Miramont |
| Missouri Heights School |
| Moffat Station |
| Monte Vista Downtown Historic District |
| Monte Vista Library |
| Montezuma Schoolhouse |
| Montezuma Valley National Bank and Store Building |
| Montgomery Court |
| Montgomery Hall, Colorado College |
| Montrose City Hall |
| Montrose County Courthouse |
| Montrose Fruit & Produce Association Building |
| Montrose Masonic Temple, Lodge No. 63 |
| Montview Boulevard Presbyterian Church |
| Monument Lake Park Building and Hatchery Complex |
| Monument Valley Park |
| Moraine Lodge |
| Moraine Park Museum and Amphitheater |
| Morgan County Courthouse and Jail |
| Morley Bridge |
| Morrison Historic District |
| Morrison Schoolhouse |
| Mosman House |
| Motor Coach Division Building-Denver Tramway Company |
| Mountainside Lodge |
| Mount Saint Scholastica Academy, East Building |
| Mount St. Gertrude Academy |
| Mt. Pleasant School |
Data from United States Park Service and Wikidata
