In 1935, Stevenson returned to Chicago to practice law. He became involved in civic activities, particularly as chairman of the Chicago branch of the Committee to defend America by Aiding the Allies from 1940 to 1941.
In 1940, Colonel Frank Knox, newly appointed by President Franklin D. Roosevelt as Secretary of the Navy, offered Stevenson a position as Principal Attorney and special assistant.
Stevenson wrote speeches, represented Colonel Frank Knox and the Navy, handled administrative duties, and