Illinois - Area of significance: Architecture
| St. James Episcopal Church |
| St. James Episcopal Church |
| St. Johns Episcopal Church |
| St. Louis Street Historic District |
| St. Luke's Hospital Complex |
| St. Mary's Church |
| St. Mary's Church of Gilberts |
| St. Matthew Evangelical Lutheran School |
| St. Nicholas Hotel |
| Stolp Island Historic District |
| Stoneleigh Manor |
| Stone Manor |
| Stone Temple Baptist Church |
| Stony Island Trust and Savings Bank Building |
| Story-Camp Rowhouses |
| Stotlar, Ed. M., House |
| St. Patrick's Roman Catholic Church |
| St. Paulus Evangelisch Lutherischen Gemeinde |
| Strauss, Jesse L., Estate |
| Strawbridge-Shepherd House |
| Strawn, Jeremiah, House |
| Strevell House |
| St. Thomas Catholic High School for Boys |
| St. Thomas Church and Convent |
| Studebaker Building |
| Sugar Creek Covered Bridge |
| Sullivan, Joseph P. O., House |
| Sunderlage Farm Smokehouse |
| Swannell, Charles E., House |
| Swedish American Telephone Company Building |
| Swedish Club of Chicago |
| Swift House |
| Swift, Louis F., House |
| Sycamore Historic District |
| Sylvan Road Bridge |
| Talman West Ridge Bungalow Historic District |
| Tanner, William A., House |
| Taylor Apartments |
| Taylor, Oscar, House |
| Taylorville Courthouse Square Historic District |
| Tazewell County Courthouse |
| Terwilliger House |
| Thebes Courthouse |
| Theosophical Society in America Headquarters |
| The Richard E. and Charlotte Henrich House |
| The Rockwell House |
| Theurer-Wrigley House |
| Third Church of Christ, Scientist |
| Thomas, F. D., House |
| Thomas, Frank, House |
| Thomas, Lewis H., House |
| Thompkins, Jennie S., House |
| Thompson, James S., House |
| Thorne, George R., House |
| Tiedemann House |
| Tiger-Anderson House |
| Tinker Swiss Cottage |
| Tomek, F.F., House |
| Town House, The |
| Town of West Belleville Historic District |
| Townsend House |
| Transfer House |
| Tree Studio Building and Annexes |
| Trinity Episcopal Church |
| Tri-Taylor Historic District |
| Trobaugh-Good House |
| Trumbull Park |
| Trustees System Service Building |
| Tudor Manor |
| Turkey Hill Grange Hall |
| Turner School |
| Twin Tower Sanctuary |
| Twiss, James C., House |
| Union Church |
| Union House |
| Union Park Congregational Church and Carpenter Chapel |
| Union Park Hotel |
| Union Station |
| Union Station |
| Union Trust Bank Company Building |
| Unitarian Church of Urbana |
| United Methodist Church of Batavia |
| United States Custom House |
| United States Housing Corporation (U.S.H.C.) Historic District |
| United States Post Office and Courthouse |
| United States Post Office and Court House |
| United States Post Office-Belvidere |
| United States Post Office-Chicago |
| Unity Church |
| Unity Temple |
| University Apartments |
| University Hall |
| University of Illinois Experimental Dairy Farm Historic District |
| Upper Alton Historic District |
| Upper Bluff Historic District |
| Uptown Broadway Building |
| Uptown Square Historic District |
| Urbana-Lincoln Hotel-Lincoln Square Mall |
| U. S. Post Office |
| U.S. Post Office |
Data from United States Park Service and Wikidata
