All - Constructed - 1930–1939
| Morristown National Historical Park |
| Morse, Robert Hosmer, House |
| Morton County WPA Bridge |
| Moton, Robert Russa, High School |
| Mounds State Park |
| Mountainair Municipal Auditorium |
| Mountain Fire Lookout Tower |
| Mountain Grove City Hall |
| Mount Cammerer Fire Lookout |
| Mount Harkness Fire Lookout |
| Mount Pleasant National Guard Armory |
| Mount Spokane Vista House |
| Mount Vernon Memorial Highway |
| Mt. Beacon Fire Observation Tower |
| Mt. Fremont Fire Lookout |
| Mt. Stella Lookout |
| Mt. Van Hoevenberg Olympic Bobsled Run |
| Muir, John, Branch |
| Muir, John, Memorial Shelter |
| Mundelein College Skyscraper Building |
| Municipal Auditorium |
| Municipal Auditorium and City Hall |
| Municipal Swimming Pool |
| Murphey School |
| Murray Theater |
| Music Mountain |
| Muskegon South Breakwater Light |
| My Old Kentucky Home |
| MYSTERY (log canoe) |
| Naco Border Station |
| Narcissa D-X Gas Station |
| Nassau County Jail |
| National Archives |
| National Guard Armory |
| National Park Service Southwest Regional Office |
| Navajo Nation Council Chamber |
| Nebraska State Capitol |
| Neillsville Post Office |
| Nelimark, Erick and Kristina, Sauna |
| Neutra, Richard and Dion, VDL Research House II |
| Neversink Valley Grange No. 1530 |
| Neville High School |
| New Deal Resources in Hawk's Nest State Park Historic District |
| New Deal Resources in Watoga State Park Historic District |
| Newkirk Water Purification Plant |
| Newton City Hall and War Memorial |
| Newton County American Legion Post No. 89 Hut |
| Newton Stadium |
| New York County Lawyers Association Building |
| Nick's Hamburger Shop |
| Nielsen-Sanderson House |
| Nishnabotna River Bridge |
| Norcatur City Hall |
| Nordlund House |
| Norris Hydroelectric Project |
| North Bend Ranger Station |
| North Casper Clubhouse |
| North Fork of the Yachats Bridge |
| North Fork Quinault Ranger Station |
| North Fork Sol Duc Shelter |
| North Little Rock Post Office |
| North Manitou Shoal Light Station |
| North Mowich Trail Shelter |
| North Rock Creek Masonry Arch Bridge |
| North Shore Sanitary District Tower |
| North Third Avenue Historic District |
| Northup Theater |
| Northwestern Electric Company-Alberta Substation |
| Notch Mountain Shelter |
| Numa Ridge Fire Lookout |
| Oak Ballroom |
| Oak Creek Irrigation Canal |
| Oak Hill School House |
| Oakland |
| Oakley High School Stadium |
| Oasis Court |
| Oatman Filling Station |
| Obsidian Cliff Kiosk |
| Ocean Spray Hotel |
| Ocmulgee National Monument |
| Ogden High School |
| Ogunquit Playhouse |
| Ohanapecosh Comfort Station No. O-302 |
| Ohanapecosh Comfort Station No. O-303 |
| Ohave Shalom Synagogue |
| Old Athens, Alabama Main Post Office |
| Old Columbia-Wrightsville Bridge |
| Old Highway 16 Bridge |
| Old Hilton Hotel |
| Old Howard Academy |
| Old-Merchants National Bank and Trust Co. Building |
| Old Stone House of Brooklyn, The |
| Old US 71-Wilton Segement |
| Old US Post Office |
| Olympus Guard Station |
| One LaSalle Street Building |
| Opus 40 |
| Oregon Caves Chateau |
| Oregon State Capitol |
| Ormond Fire House |
Data from United States Park Service and Wikidata
