Ohio - Area of significance: Architecture
| Somerset Historic District |
| Sorrick-Oster Store |
| South Brooklyn Commercial District |
| South Charleston Historic District |
| South Crescent Arms, The |
| Southern Ohio Lunatic Asylum |
| South Fountain Avenue Historic District |
| South High Street Commercial Grouping |
| Southington Township School |
| South Lincoln Avenue Historic District |
| South Main Street District |
| South Main Street District |
| South Main Street Historic District |
| South Park Historic District |
| South Ridge Schoolhouse |
| South Salem Academy |
| South Sandusky Avenue Historic District |
| South School |
| South South Street Historic District |
| Southworth House |
| Spafford House |
| Speaker, Charles, House |
| Spencer's Landing |
| Spencer Town Hall |
| Spitler, Samuel, House |
| Spitzer Building |
| Sprague-Deaver House |
| Sprague House |
| Sprague, Jonathan, House |
| Spread Eagle Tavern-Conrey, James D., House |
| Springboro Historic District |
| Springdale |
| Springfield Country Club |
| Springfield Downtown Historic District |
| Spring Grove Cemetery |
| Spring Grove Cemetery |
| Spring Grove Cemetery Chapel |
| Spring Grove Historic District |
| Square 13 Historic District |
| Squire's Glen Farm |
| Squirrel-Forrest Historic District |
| St. Adalbert Polish Catholic Church |
| Stadium Square Historic District |
| Stagecoach Inn |
| Stager-Beckwith House |
| Staley Farm |
| Staley, Mr. and Mrs. Karl A., House |
| St. Aloysius Catholic Church |
| St. Aloysius-on-the-Ohio |
| Stambaugh Building |
| Stambaugh, Henry H., Memorial Auditorium |
| Stanbery, Edwin, Office |
| Standart-Simmons Hardware Company |
| St. Andrew's Episcopal Church |
| Stanford, George, Farm |
| Stang, John, House |
| Stan Hywet Hall-Frank A. Seiberling House |
| Stan Hywet Poultry Keepers Cottage |
| Stanley Block |
| St. Ann Roman Catholic Church Complex |
| St. Anthony Catholic Church, Padua |
| Stanton Farm |
| Stark County Courthouse and Annex |
| Starr, Horace C., House and Carriage Barns |
| Starr-Truscott House |
| State Theater |
| St. Augustine Catholic Church |
| St. Augustine's Catholic Church |
| St. Bernard Catholic Church and Rectory |
| St. Bernard's Church |
| St. Boniface Roman Catholic Church, School, Rectory, and Convent of the Sister of the Precious Blood |
| St. Charles Seminary and Chapel |
| St. Clair Hospital |
| St. Clair Street Historic District |
| St. Clairsville Historic District |
| Steamboat Hotel |
| Stearns, Edward R., House |
| Stearns, William, House |
| Stedman-Shafer Grocery Warehouse Building |
| Steele's Hill-Grafton Hill Historic District |
| Steindam House |
| Steinkamp, Joseph G. House |
| St. Elizabeth's Magyar Roman Catholic Church |
| Stengel, John S., House |
| Steubenville Commercial Historic District |
| Steubenville YMCA Building |
| Stevenson, Joshua, House |
| Stewart-Hanson Farm |
| Stewart, Harry Bartlett, Property |
| Stewart Towers |
| St. Francis Catholic Church and Rectory |
| St. Francis De Sales Church Historic District |
| St. Francis Hospital |
| St. Francis Seminary |
| St. Francis Xavier Church |
| St. George Parish and Newman Center |
| St. Henry Catholic Church |
| St. Henry Roman Catholic Church and Rectory |
| St. Ignatius High School |
| Stites House |
Data from United States Park Service and Wikidata
