Ohio - Criteria: C (architecture/engineering)
| Leipsic City Hall |
| Lerner Building |
| Lersch, John, House |
| Levering Hall |
| Levy, Harry Milton, House |
| Levy, Soloman, House |
| Lewis, Dr. A. C., House |
| Lewis, Samuel, Farmhouse |
| Lewis, Samuel, House |
| Libbey, Edward Drummond, High School |
| Liberty Theatre |
| Licking County Courthouse |
| Ligget, J., Residence |
| Liggett-Freedlander House |
| Light, Jacob, House |
| Lilley, Robert D., House |
| Lillybanks |
| Lilly House |
| Lima Cleaning and Pressing Company |
| Lima Memorial Hall |
| Lima Pennsylvania Railroad Passenger Depot |
| Lima Stadium |
| Limbach Block Historic District |
| Limestone Vale |
| Linaweaver, Dr. Albert, House |
| Lindner Building |
| Lindsey Building |
| Linneman Building |
| Lisbon Historic District |
| Lloyd, John Uri, House |
| Lockington Covered Bridge |
| 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 |
| Lockwood, J. C., House |
| Loew-Define Grocery Store and Home |
| Loew's Theatre |
| Logan City Hall |
| Logan County Courthouse |
| Lombardy Apartment Building |
| London Commercial Business Historic District |
| Long and Third Commercial Building |
| Longenecker, Doctor, Office Building |
| Long-Mueller House |
| Look About Lodge |
| Looker, Othniel, House |
| Lorain-Carnegie Bridge |
| Lorain County Courthouse |
| Lorain Fire Station No. 1 |
| Lorain Lighthouse |
| Lord, Addison, House |
| Lovejoy, Carrie, House |
| Loveridge, Richard and Ann, House |
| Lower Price Hill Historic District |
| Lowler's Tavern |
| Lowrie, S. Gale and Agnes P., House |
| Lucas County Courthouse and Jail |
| Lucas County Hospital and Nurse's Home |
| Luelleman, William, House |
| Luethstrom-Hurin House |
| LuNeack House |
| Lunkenheimer, Frederick, House |
| Lutz-Martin Farm |
| Lutz's Tavern |
| Lyman, William, House |
| Lynchburg Covered Bridge |
| Lynnwood Farm |
| Lytle Park Historic District |
| MacDonell House |
| Macedonia Church |
| Mace, Henry, House |
| Mackinaw Historic District |
| Macksville Tavern |
| Macomb, Mary Worthington, House |
| Madam Fredin's Eden Park School and Neighboring Row House |
| Madison and Woodburn Historic District |
| Madison County Courthouse |
| Madison Seminary And Home |
| Madison-Stewart Historic District |
| Mad River Block |
| Magnolia-Wade Park Historic District |
| Magruder Building |
| Mahoning County Courthouse |
| Mahoning National Bank Building |
| Main and Third Street Cluster |
| Main-Market Historic District |
| Malio House |
| Maltby, Henry, House |
| Mansfield Savings Bank |
| Mansfield Woman's Club |
| Mantua Center School |
| March, George, House |
| Mardot Antique Shop |
Data from United States Park Service and Wikidata
