Ohio - Significance region: Local
| Third National Bank |
| Thomas, Dr. Kersey G., House and Office |
| Thomas Manufacturing Company Warehouse |
| Thomas Select School |
| Thompson-Builder House |
| Thompson-Bullock House |
| Thompson, Cassius Clark, House |
| Thompson, Enoch, House |
| Thornton-Guise Kitchen And House |
| Thorp, Manville, Residence |
| Thorp, W. A., House |
| Thrush, Morgan, Farm Complex |
| Thurston Building |
| Tiedemann, Hannes, House |
| Tiffin Agricultural Works |
| Tiffin Art Metal Company |
| Tiffin Waterworks |
| Tilden, Daniel, House |
| Times Building-Lodge Hall |
| Timken Vocational High School |
| Tinnerman Steel Range Company |
| Tod Homestead Cemetery Gate |
| Toledo and Ohio Central Depot |
| Toledo and Ohio Central Railroad Station |
| Toledo Central Business Historic District |
| Toledo City Market |
| Toledo Club |
| Toledo Olde Towne Historic District |
| Toledo Traction Company Power Station |
| Toledo Yacht Club |
| Tosheff's Restaurant and Hotel |
| Towers Hall, Otterbein College |
| Tower Site |
| Town Center District |
| Townes, Clayton, House |
| Town Hall |
| Town Pump of East Sparta, The |
| Townsend, William T., House |
| Traction Company Building |
| Travelers Hotel |
| Travellers' Rest Inn |
| Traxler Mansion |
| Tremaine-Gallagher Residence |
| Tremont Historic District |
| Tremont House |
| Trevey Mound (33WA193) |
| Trimble, James S., House |
| Trinity Cathedral |
| Trinity Cathedral Church Home |
| Trinity Episcopal Church |
| Trinity Episcopal Church |
| Trinity German Evangelical Lutheran Church |
| Trinity Lutheran Church |
| Tripp-Bauer Building |
| Trop Farm |
| Trotwood Railroad Station and Depot |
| Tubbs-Sourwine House |
| Tuscarawas Avenue-Alexander Square Commercial Historic District |
| Tuttle House |
| Twelve Mile House |
| Twentieth Century Theatre |
| Twin Arch Stone Culvert |
| Twin Oaks |
| Twinsburg Congregational Church |
| Twinsburg Institute |
| Ufferman Site |
| Ulyatt, Abraham, House |
| Umsted Farm |
| Underwood Farms Rural Historic District |
| Underwriters Salvage Corps |
| Unger, George B., House |
| Union Baptist Cemetery |
| Union Block |
| Union Cemetery-Beatty Park |
| Union Chapel |
| Union Church |
| Union Club |
| Union, Old, School Building |
| Union Steel Screw Office Building |
| Union Township Works II |
| Union Trust Building |
| Unionville District School |
| Unionville Tavern |
| Uniopolis Town Hall |
| United Brethren in Christ |
| United Brethren Publishing House |
| United Church of Huntington |
| United Colored American Cemetery |
| United Methodist Church |
| United Methodist Church |
| United Motor Service Building |
| United States Carriage Company |
| United States Courthouse and Custom House |
| United States Playing Card Company Complex |
| United States Post Office |
| United States Post Office and Courthouse |
| United States Post Office and Court House |
| Universalist Church Of Westfield Center |
| Universal Terminal Company Dock and Warehouse |
| University Club |
Data from United States Park Service and Wikidata
