The Ernest Horn Papers reflect his research and publications in geography, history, and other social science education  spelling, and vocabulary. Organizations prominently represented include the American Historical Association Commission on the Social Studies, the Canada - United States Committee on Education, the University of Iowa University Elementary School, and other schools where Horn studied or taught. Correspondents include Charles A. Beard (letters currently cataloged as Special Collections manuscripts), Madeline Darrough Horn, and University of Iowa education deans and presidents.