Hook was nominated by President Theodore Roosevelt on November 10, 1903, to a joint seat on the United States Court of Appeals for the Eighth Circuit and the United States Circuit Courts for the Eighth Circuit vacated by Judge Henry Clay Caldwell. He was confirmed by the Senate on November 17, 1903, and received his commission the same day. On December 31, 1911, the Circuit Courts were abolished and he thereafter served only on the Court of Appeals. His service terminated on August 11, 1921, due to his death in Sayner, Wisconsin.
