Correspondence, memoranda, reports, subject and legislative files, speeches and articles, patronage and constituent files, notebooks, newspaper clippings, and other material relating primarily to Borah's political interests and career in the U.S. Senate. The papers document the principal issues of politics and foreign and domestic policy during the period 1912-1940, especially antitrust legislation, League of Nations and World Court, isolationism, foreign relations with the Soviet Union, land utilization, New Deal and National Recovery Administration, Sino-Japanese War, Lausanne treaty settlement, neutrality legislation, and outlawry of war. Also includes material on Idaho politics and and a 1936 attempt to secure Borah the Republican presidential nomination.

Correspondents include Jane Addams, Edwin Montefiore Borchard, Henry M. Dawes, Leonidas Carstarphen Dyer, Hamilton Fish, Samuel Gompers, Norman Hapgood, Will H. Hays, John Haynes Holmes, James Weldon Johnson, Frank B. Kellogg, Frank Knox, Henry Cabot Lodge, Amos Pinchot, Gifford Pinchot, Raymond Robins, Franklin D. Roosevelt, Thomas Joseph Walsh, William Allen White, and Woodrow Wilson.