To make the best use of your time, please explore the library archive website.
State Historical Society of Iowa Collections Description
Here is a direct link to the catalog: Research Center Catalog
Directions: Take I35 to 235 and continue on 235 West in Des Moines to E. 6th Street exit. Go south (left) on E. 6th to E. Locust Street. The State Historical Museum is the corner of E. 6th and E. Locust. Street parking is available in the area.
While the State Historical Society Library holds predominately Iowa materials, there are selections from other states as well. Whether your research is Iowa based or not, this is an opportunity to learn about archive holdings in any state.