Correspondence, memoranda, speeches, articles, reports, notebooks, legislative files, subject files, patronage and constituent files, newspaper clippings, and other papers relating primarily to Borah's political interests and career in the U.S. Senate. Documents national politics and foreign and domestic policy during the period 1912-1940. Subjects include agriculture, antitrust legislation, constitutional interpretation, disarmament, foreign relations with the Soviet Union, isolationism, land utilization, the Lausanne treaty settlement, military activities in Latin America, League of Nations, neutrality legislation, New Deal and National Recovery Administration, Permanent Court of International Justice (World Court), the Red Scare, Franklin D. Roosevelt, Sino-Japanese War, U.S. Army affairs, universal military training, and outlawry of war. Other subjects include Idaho state politics and a 1936 attempt to secure Borah the Republican presidential nomination. Includes correspondence (1923-1936) of Borah's secretary, Grace Hileman.

Correspondents include Jane Addams, Edwin Borchard, Henry M. Dawes, Leonidas Carstarphen Dyer, Evan A. Evans, Hamilton Fish, James H. Gipson, Samuel Gompers, Frank Robert Gooding, Norman Hapgood, John W. Hart, James H. Hawley, Will H. Hays, John Haynes Holmes, James Weldon Johnson, Frank B. Kellogg, Frank Knox, Henry Cabot Lodge, Ray McKaig, Amos Pinchot, Gifford Pinchot, Raymond Robins, Irvin E. Rockwell, Franklin D. Roosevelt, Thomas Joseph Walsh, William Allen White, and Woodrow Wilson.