Byrnes represented South Carolina in the House of Representatives (1911-25) and the Senate (1931-41), before his friend and long-time political ally Franklin Roosevelt appointed him to the Court in July 1941. Byrnes was the last person appointed to the Supreme Court who did not attend law school, but instead was admitted to practice by reading law. His tenure on the Court was brief: 15 months after taking his seat, Roosevelt asked him to resign, in order to head up the Office of Economic Stabilization (which later became the Office of War Mobilization). In this role, with Roosevelt's acquiescence, Byrnes' authority within the government grew, as he assisted the President far and wide.
Following Roosevelt's death, Byrnes was one of Harry Truman's closest advisers (they had joined forces in the Senate), and in July 1945, Truman appointed Byrnes the 49th Secretary of State. But their relationship grew strained, and Byrnes resigned in January 1947. In 1950, he was elected governor of South Carolina, serving one term.
Byrnes is one of the few people to serve in all three branches of the government, as well as a leadership position in his own state.