Wisconsin - Criteria: A (event)
| Martens, Julius J., Company Building |
| Masonic Temple |
| Masonic Temple Building |
| Mathias Mitchell Public Square-Main Street Historic District |
| Mazomanie Downtown Historic District |
| Mazomanie Town Hall |
| McCaffary, John, House |
| McClurg Building |
| McCord Village |
| McCormick-International Harvester Company Branch House |
| McCoy Farmhouse |
| McFarland House |
| McIntosh-Goodrich Mansion |
| Medford Free Public Library |
| Melchoir Hotel and Brewery Ruins |
| Mellen City Hall |
| Memorial Hall |
| Menomonie Downtown Historic District |
| Merrill City Hall |
| Merrimac Ferry |
| METEOR (Whaleback carrier) |
| Middleton Depot, Chicago, Milwaukee, and St. Paul Railroad |
| Milton College Historic District |
| Milton House |
| Milwaukee Breakwater Light |
| Milwaukee County Courthouse |
| Milwaukee County Dispensary and Emergency Hospital |
| Milwaukee County School of Agriculture and Domestic Economy Historic District |
| "Milwaukee-Downer ""Quad""" |
| Milwaukee Falls Lime Company |
| Milwaukee Hospital |
| Milwaukee Normal School-Milwaukee Girls' Trade and Technical High School |
| Milwaukee Pierhead Light |
| Milwaukee Road Depot |
| Milwaukee Road Passenger Depot |
| MILWAUKEE (steam screw) Shipwreck |
| Mindoro Cut |
| Mission House Historic District |
| Mitchell Building |
| Monroe Commercial District |
| Monroe Water Tower |
| Montello Commercial Historic District |
| Montreal Company Location Historic District |
| Moon, D. R., Memorial Library |
| Moquon Town Hall and Fire Station Complex |
| Mountain Fire Lookout Tower |
| Mountain School |
| Mount Horeb Public School |
| Mt. Horeb Opera Block |
| Muirdale Tuberculosis Sanatorium |
| Murphy Farms Number 1 |
| Myers, Peter, Pork Packing Plant and Willard Coleman Building |
| Namur Belgian-American District |
| Nashold 20-sided Barn |
| Near East Side Historic District |
| Neillsville Downtown Historic District |
| Neillsville Standpipe |
| New Glarus Town Hall |
| New Richmond News Building |
| New Richmond West Side Historic District |
| NIAGARA (steamer) |
| No. 4 Engine House |
| North Grant Boulevard Historic District |
| North Hall-River Falls State Normal School |
| North Hall, University of Wisconsin |
| North Point Lighthouse |
| North Sherman Boulevard Historic District |
| North Third Street Historic District |
| Northwestern Branch, National Home for Disabled Volunteer Soldiers Historic District |
| North Wisconsin Lumber Company Office |
| Oak Creek Parkway |
| Oconomowoc City Hall |
| Oconomowoc Depot |
| Okauchee House |
| Old Executive Mansion |
| Old Fourth Ward Historic District |
| Old Indian Agency House |
| Old Iron County Courthouse |
| Old Main Street Historic District |
| Old Rock School |
| Old Rock School |
| Old Spring Tavern |
| Old St. Mary's Church |
| Old Synagogue |
| Old U.S. Forest Products Laboratory |
| Old World Third Street Historic District |
| Omaha Hotel |
| Omro Village Hall and Engine House |
| Oneida Street Station |
| Oregon Masonic Lodge |
| Orfordville Depot |
| Orpheum Theater |
| Orton Park |
| Orville Beach Memorial Manual Training School |
| Oshkosh Grand Opera House |
| Oshkosh State Normal School Historic District |
| OTTAWA (Tug) Shipwreck Site |
| Otter Spring House |
| Oviatt House |
| Owen High School |
Data from United States Park Service and Wikidata
