National Register of Historical Places - Marshall County
- Provides a listing of properties, districts, and landmarks in the county. Includes architectural style and period of significance.
- http://www.historicdistricts.com/IA/Marshall/state.html

The Political Graveyard: Marshall County, Iowa
- Database provides political history, cemetery locations, and brief biographies of politicians who were born, lived or died in the county.
- http://politicalgraveyard.com/geo/IA/MA.html#BORN

Historical Society of Marshall County
- Collects, stores and preserves artifacts and documents that were used or manufactured in the county. Includes a virtual museum and a membership form.
- http://www.marshallhistory.org/