Ohio - Significance region: Local
| Mount Adams Public School |
| Mountain House |
| Mount Airy Forest |
| Mount Auburn Historic District |
| Mount Auburn School |
| Mount Liberty Tavern |
| Mount Orab Station |
| Mount Sterling Historic District |
| Mount Union College District |
| Mount Victory Historic District |
| Mount Zion Baptist Church |
| Mount Zion Presbyterian Church |
| Mt. Healthy Public School |
| Mt. Tabor Church Building, Cemetery and Hitching Lot |
| Mueller Brewery |
| Mueller, Christ, House |
| Mueller Electric Company Building |
| Muller, Daniel C., Carousel |
| Mumma, Jacob H. W., House |
| Municipal Building |
| Municipal Light Plant |
| Munson, Judge Albert, House |
| Murray Hill School |
| Murschel House |
| Musser, Henry, House |
| Mutual Home & Savings Association Building |
| Myer House |
| Myers Block-Home Company Building |
| Myers Daily Market |
| Myrtle-Highview Historic District |
| Nafzger-Miller House |
| Nashport Mound |
| Nathaniel Hawthorne Elementary School |
| National Home, Daughters of America |
| National Town and Country Club |
| Neal Clothing |
| Neal Terrace |
| Near Northside Historic District |
| Neely-Sieber House |
| Neff Apartments |
| Neff, Conrad, House |
| Neff, Edward E., House |
| Nelson, Luman, House |
| Nelsonville Historic District |
| Neukom, Albert, House |
| Newark Downtown Historic District |
| Newark High School |
| New Baltimore Inn |
| Newberry Township School |
| Newcom House |
| New Concord-Union High School |
| New England Building |
| New Garden Monthly Meetinghouse |
| New Hayden Building |
| New Indianola Historic District |
| Newlove Works |
| New Lyme Institute |
| New Lyme Town Hall |
| Newman, William, House |
| New Market Township Community House |
| Newport and Cincinnati Bridge |
| Newport Village Allotment Historic District |
| New Richmond Water Works and Electric Station |
| New Straitsville School |
| Newton Avenue Historic District |
| Newton, Judge Eben, House |
| New York Central Freight House |
| Nichols, Eli, Farm |
| Nichols, John H., House |
| Nicholson, James, House |
| Nichols, Walter, House |
| Nickel, Old, Plate Railroad Depot |
| Niles Masonic Temple |
| Nimocks House |
| Ninth Street Historic District |
| No. 5 Fire Station |
| Noble County Jail and Sheriff's Office |
| Noble, Jonathan, House |
| Noble, Lewis, House |
| Nooney, William , House |
| Norfolk and Western Freight Station |
| Norfolk And Western Railroad Depot |
| Normandy Farms |
| North Baltimore Town Hall |
| North Columbus Commercial Historic District |
| Northeast Tiffin Historic District |
| North End Neighborhood Historic District |
| Northern Ohio Blanket Mills |
| Northfield Town Hall |
| North High School |
| North High Street Historic District |
| North Hill Historic District |
| North Main-North Detroit Street Historic District |
| North Main-North Gay Streets Historic District |
| North Market Historic District |
| North Olmsted Town Hall |
| North Presbyterian Church |
| North Ridgeville City Hall |
| Northrop, Julia Carter, House |
| North Sandusky Street Historic District |
Data from United States Park Service and Wikidata
