Senator Pepper drew national attention in 1922 by successful mediating an anthracite coal strike. He served on the Military Affairs, Naval Affairs, and Foreign Relations committees, and became chairman of the committees on Banking and Currency and the Library of Congress. He tried to allow the United States to join the World Court but not the League of Nations, and considered this proposal one of his greatest accomplishments, including it as an appendix to his autobiography even though the proposal was later watered down.