Iowa - Area of significance: Exploration/Settlement
| Sharon, Fred B., House |
| Sharon Methodist Episcopal Church |
| Sheldahl First Norwegian Evangelical Lutheran Church |
| Siemer House |
| Smith, Hiram C., House |
| Smith, Hiram C., Milking Shed |
| Smith, James J. and Anna J. (Linean), House #1 |
| Sprague, Brown, and Knowlton Store |
| Spring Creek Friends Cemetery |
| St. Anthony's Roman Catholic Church Complex |
| St. George's Episcopal Church |
| St. John's Lutheran Church |
| St. Joseph's Catholic Church |
| St. Joseph's Roman Catholic Church and Cemetery Historic District |
| St. Mary's Roman Catholic Church Complex |
| Stone House |
| St. Patrick Church |
| St. Patrick's Church |
| Stratton House |
| Swedish Baptist Church |
| Tabor Antislavery Historic District |
| Tabor Congregational Church |
| Taft, Stephen Harris, House |
| Tidrick, Miller Richard and Mary Fisher, House |
| Tuttle, Thomas F. and Nancy, House |
| Van Loon, Dirk, House |
| Vawter, J. G. and Elizabeth S., House |
| Waln, Elijah D. and Mary J. (Adams), House |
| Washington Park |
| Washington Prairie Methodist Church |
| Wasson, Dr. Jesse, Building |
| Weber House |
| Webster, Dickinson, House |
| Wehmer House |
| White, H. A., General Store and House |
| White, Munger and Company, Store |
| Wickiup Hill Late Woodland Village Site |
| Wickiup Hill Middle to Late Archaic Camp Site |
| Wickiup Hill Mound Group No. 1 |
| Wilds, Col. John Q. and Rowena (Camp), House |
| Wilson, Anson, House |
| Wilson, Paton and Hannah, House |
| Wilson, Seth and Elizabeth, House |
| Wood, Jeremiah, House |
| Wood, William Kennison, House |
Data from United States Park Service and Wikidata
