Ohio - Criteria: A (event)
| Lawndale Farm Complex |
| League Park |
| Lebanon Academy |
| Lebanon Cemetery Entrance Arch |
| Lebol, John, House, Smokehouse and Springhouse |
| Lehman, Abraham, Farmhouse |
| Leipsic City Hall |
| Levering Hall |
| Levy, Soloman, House |
| Libbey, Edward Drummond, High School |
| Lima Memorial Hall |
| Lima Pennsylvania Railroad Passenger Depot |
| Limbach Block Historic District |
| Lincoln Theatre |
| Lindner Building |
| Lindsey Building |
| Lion Knitting Mills |
| Lisbon Historic District |
| Lockington Locks Historical Area |
| Lock No. 26 |
| Lock No. 27 |
| Lock No. 28 |
| Lock No. 31 |
| Lock No. 32 |
| Lock No. 33 |
| Lock No. 34 |
| Lock No. 35 |
| Lock Tender's House and Inn |
| Lockville Canal Locks |
| Loew-Define Grocery Store and Home |
| Loew's Theatre |
| Long-Romspert House |
| Look About Lodge |
| Lorain-Carnegie Bridge |
| Lorain Fire Station No. 1 |
| Lorain Lighthouse |
| Lorain YMCA Building |
| Lotz, Henry, Stone |
| Lovejoy, Carrie, House |
| Lowellville Railroad Station |
| Lubal Manufacturing and Distributing Company, The |
| Lucas County Hospital and Nurse's Home |
| Lutz-Martin Farm |
| Lyle, Samuel, Log House |
| Lytle Park Historic District |
| Macedonia Church |
| Macksville Tavern |
| Macomb, Mary Worthington, House |
| Madison and Woodburn Historic District |
| Madison Seminary And Home |
| Mad River Block |
| Magnolia-Wade Park Historic District |
| Mahoning National Bank Building |
| Main and Third Street Cluster |
| Main-Market Historic District |
| Main Theatre |
| Malabar Farm |
| Maltby, Henry, House |
| Manasseh Cutler Hall, Ohio University |
| Mantua Center School |
| Marblehead Lighthouse |
| March, George, House |
| Marion Cemetery Receiving Vault |
| Marion Township School District No. 3 |
| Marion Township Sub-District #8 School |
| Marlow Theatre |
| Marmon, Martin, House |
| Marquart-Mercer Farm |
| Marshall, James E., House |
| Martin, Henry, Farm |
| Marvin Memorial Library |
| Masonic Lodge #472 |
| Masonic Temple |
| Masonic Temple |
| Masonic Temple |
| Masonic Temple |
| Masonic Temple Building |
| Masonic Temple Building |
| Masonic Temple Price Hill Lodge, No. 524 |
| Mason, John Wesley, Gothic Cottage |
| Massillon Downtown Historic District |
| Mather, Flora Stone, College District |
| Maumee Sidecut |
| May 4, 1970, Kent State Shootings Site |
| May Company |
| May, David and Mary, House |
| Mayfield Theatre Building, The |
| McCafferty Run Farmstead |
| McCarthy-Blosser-Dillon Building |
| McCormick Manufacturing Company Building |
| McCrory Building |
| McDonald Farm |
| McKay, Moses, House |
| McKever, Lewis, Farmhouse |
| McKinley Memorial |
| McKinley School |
| McKisson, Robert, House |
| Mecklenburg's Garden |
| Medical Centre Building |
| Medina County Courthouse |
Data from United States Park Service and Wikidata
