Indiana - Criteria: C (architecture/engineering)
| Morton School |
| Moscow Covered Bridge |
| Mount Vernon Downtown Historic District |
| Mountz House |
| Mount Zion Methodist Episcopal Church |
| Mt. Pisgah Lutheran Church |
| Muncie Public Library |
| Murray Theater |
| Myrtle Fern |
| Nappanee West Park and Pavilion |
| Nappaness Eastside Historic District |
| Narrows Bridge |
| Neely House |
| Neet Bridge |
| Nelson, F.P., House |
| Nevins Bridge |
| New Albany Downtown Historic District |
| Newberry Friends Meeting House |
| Newby, Micah, House |
| New Carlisle Historic District |
| New Castle Commercial Historic District |
| New Goshen District No. 2 School |
| New Hope Bridge |
| Newman, M. G., Building |
| Newport Covered Bridge |
| Newsom-Marr Farm |
| Newton County Courthouse |
| New York Central Railroad Passenger Depot |
| New York Chicago and St. Louis Railroad Steam Locomotive No. 765 |
| Nichols, Charles E., House |
| Nichols, J.L., House and Studio |
| Nicholson, Andrew, Farmstead |
| Nicholson-Rand House |
| Niewerth Building |
| Ninde-Mead-Farnsworth House |
| Ninth Street Hill Neighborhood Historic District |
| Noble County Courthouse |
| Noble County Sheriff's House and Jail |
| Noblesville Commercial Historic District |
| Noblesville Milling Company Mill |
| Noftzger-Adams House |
| Normal Hall |
| Norris Farm-Maxinkuckee Orchard |
| Norris Ford Covered Bridge |
| North Anthony Boulevard Historic District |
| North Christian Church |
| Northern States Life Insurance Company |
| North Irvington Gardens Historic District |
| North Jefferson Street Historic District |
| North Liberty Commercial Historic District |
| North Liberty Park |
| North Manchester Covered Bridge |
| North Manchester Historic District |
| North Manchester Public Library |
| North Meridian Street Historic District |
| North Pumping Station |
| Northside Boulevard Riverwall |
| North Vernon Downtown Historic District |
| North Wabash Historic District |
| North Washington Street Historic District |
| Northwood Historic District |
| Norton, C. S., Mansion |
| Nurses' Sunken Garden and Convalescent Park |
| Oakdale Historic District |
| Oakdale School |
| Oak Hill Cemetery |
| Oak Hill Cemetery |
| Oaklandon Historic District |
| O'Donnell Building |
| Offutt Covered Bridge |
| O'Hair, James Edington Montgomery, House |
| Ohio Boulevard-Demming Park Historic District |
| Ohio Street Bridge |
| Old Bittermann Building |
| Old Cathedral Complex |
| Old Courthouse (Second St. Joseph County Courthouse) |
| Old Crescent, The |
| Old East Historic District |
| Oldenburg Historic District |
| Olde Store (John O'Ferrell Store) |
| Old Fellwock Auto Company |
| Oldfields |
| Old Frankfort Stone High School |
| Old Greencastle Historic District |
| Old Hoosier Theatre |
| Old Jeffersonville Historic District |
| Old Newburgh Presbyterian Church |
| Old Northside Historic District |
| Old Perry County Courthouse |
| Old Plat Historic District |
| Old Richmond Historic District |
| Old Silk Stocking Historic District |
| Old State Bank |
| Old Timbers |
| Old Vanderburgh County Courthouse |
| Old Warrick County Jail |
| Old West End Historic District |
| Oliver, Joseph D., House |
| O'Neall, Abijah II, House |
| Opel, John, House |
Data from United States Park Service and Wikidata
