Iowa - Criteria: C (architecture/engineering)
| Suiter, Jacob, House |
| Summit Apartment Building |
| Sumner Bridge |
| Sumner High School |
| Sumner School |
| Sunday, Robert H., House |
| Surf Ballroom |
| Sutliff Bridge |
| Swan, George B., House |
| Swedesburg Historic Commercial District |
| Swedish Evangelical Lutheran Church |
| Swigert, W. B., House |
| Sylvan Theater Historic District |
| Syndicate Block |
| Syndicate Block |
| Tabor Congregational Church |
| Taft, Stephen Harris, House |
| Taft-West Warehouse |
| Tama County Courthouse |
| Taubman, Henry, House |
| Taylor County Courthouse |
| Taylor's Ford Bridge |
| Taylor-Van Note |
| Taylor, Wenzil, Building |
| Teachout Building |
| Tedford, W. H., House |
| Temple, Marcellus Luther and Julia Protzman, House |
| Templeton, I. Edward, House |
| Ten Hagen Cottage-Stegman Store |
| Terrace Hill |
| Terrace Park Historic District |
| Tevoet, Lambert, House |
| The Capitol Theater |
| Thedinga, J. H., House |
| Theodore Roosevelt High School |
| The Park Place-Grand Avenue Residential District |
| Third Street Bridge (FHWA No. 012250) |
| Thompson, Charles J., House |
| Thomsen Round Barn |
| Tidrick, Miller Richard and Mary Fisher, House |
| Timmerman-Burd Building |
| Tipton State Bank |
| Torrance House |
| Town Clock Building |
| Trappers Bay State Park Picnic Shelter |
| Tremaine Bridge |
| Trent-Beaver House |
| Trier, Paul J. and Ida, House |
| Trimble-Parker Historic Farmstead District |
| Trinity Episcopal Cathedral |
| Trinity Episcopal Church |
| Trinity Episcopal Church |
| Trinity Memorial Episcopal Church |
| Trinity Methodist Episcopal Church |
| Tromley, George, Jr., House |
| Tulleys, Lysander, House |
| Turner, Francis A. and Rose M., House |
| Turner, Fred G., House |
| Turner, Susie P., Double House |
| Tuttle, Thomas F. and Nancy, House |
| Twin Bridge |
| Twombley, Voltaire, Building |
| Tyden Farm No. 6 Farmstead Historic District |
| Ulysses Simpson Grant Elementary School |
| Union Bakery |
| Union Block |
| Union Brewery |
| Union Cemetery Gardener's Cottage |
| Union Electric Telephone & Telegraph |
| Union Presbyterian Church |
| Union Savings Bank and Trust |
| Union Sunday School |
| United Presbyterian Church, Summerset |
| United States Post Office and Courthouse |
| United States Post Office and Court House |
| Universalist Church |
| Untiedt, Claus, House |
| Upper Bluffton Bridge |
| Upper Central Avenue Commercial Historic District |
| Upper Iowa River Bridge |
| Upper Iowa Street Historic District |
| Upper Main Street Historic District |
| Upper Paradise |
| Upper Paris Bridge |
| Upper Stone Schoolhouse |
| U. S. Post Office |
| U.S. Post Office |
| U.S. Post Office |
| U.S. Post Office |
| U.S. Post Office and Courthouse |
| US Post Office-Iowa Falls |
| Valley Junction Commercial Historic District |
| Van Allen Store |
| Van Asch, William, House-Huibert Debooy Commercial Room |
| Van Buren County Courthouse |
| Van Den Berg, Hendrik J. and Wilhelmina H., Cottage |
| Vander Veer Park Historic District |
| Vander Wilt, Dirk and Cornelia J., Cottage |
| Van Maren, Henry and Johanna, House-Diamond Filling Station |
| Van Spanckeren, B. H. and J. H. H., Row Houses |
Data from United States Park Service and Wikidata
