Governor and U.S. Senator from Iowa. The papers primarily consist of political speeches and correspondence on topics ranging from neutrality to the Democratic conventions.

U.S. Senator from Iowa , and educator. Arranged in 9 series, the papers consist of subject files, casework files, issue statements, clippings, audio, visual, film and photographs during his term in office. Subjects of special concern to Clark range from Africa and international relations to agriculture and conservation, Democratic Party politics to the aged, and education to transportation.

Governor and U.S. Senator from Iowa. Gubernatorial and senatorial office files relating to his political career.