Ohio - Area of significance: Industry
| Sidney Walnut Avenue Historic District |
| Smucker, J.M., House |
| South Fountain Avenue Historic District |
| South Main Street District |
| South Park Historic District |
| Spicer Manufacturing Building |
| Springfield Metallic Casket Company |
| Staley Farm |
| Stan Hywet Hall-Frank A. Seiberling House |
| Stearns, Edward R., House |
| Stearns, William, House |
| Steubenville Pottery Company Buildings |
| Stockbridge Apartment Building |
| Stoffel, Henry, Blacksmith Shop |
| Stoneman, Joseph, House |
| Stratford Methodist Episcopal Church |
| Stump, John, House And Mill |
| Superior Avenue Historic District |
| Tangeman, John, House |
| Thomas Manufacturing Company Warehouse |
| Thompson, Cassius Clark, House |
| Thomson, Peter G., House |
| Tiffin Agricultural Works |
| Tiffin Art Metal Company |
| Tiffin Waterworks |
| Timken Vocational High School |
| Tinnerman Steel Range Company |
| Union Steel Screw Office Building |
| United States Carriage Company |
| United States Playing Card Company Complex |
| Van Rooy Coffee Company Building |
| Vesuvius Furnace |
| Village Historic District |
| Village of Addyston Historic District |
| Wadsworth Downtown Historic District |
| Wagner Brothers Bottling Works |
| Wallace Farm |
| Ward-Thomas House |
| Warner & Swasey Company Building |
| Waverly Canal Historic District |
| Webster Manufacturing |
| Wells-Clark-Strouss House |
| West 25th Street-Detroit Avenue Historic District |
| West Fourth Street Historic District (Amendment) |
| West Side Planing Mill (rear) |
| Weustoff and Getz Company |
| White Chewing Gum Company Building |
| White's-Vale Mill |
| White, Walter C., Estate |
| Whitney, George W., House |
| Williams, Henry Harrison, House |
| Wintzer, Charles, Building |
| Woodland Avenue and West Side Railroad Powerhouse |
| W.P. SNYDER, JR. (steamboat) |
| Wright Company Factory |
| Wright, Potter, House |
| Youngstown Foundry and Machine East Boardman Works |
Data from United States Park Service and Wikidata
