He is also listed as a Mason, but that is not as easy to prove for Stimson as it is for Truman.
http://www.freemasonrywatch.org/politics_masonry.html
President Harry Truman, a Past Grand Master of the Grand Lodge of Missouri, was quoted as saying: "Although I hold the highest civil honor in the world, I have always regarded my rank and title as a Past Grand Master of Masons as the greatest honor that has ever come to me."
Following President Truman's death in 1972, the Scottish Rite Grand Commander hailed the Missouri-born Chief Executive as "a devoted son" of the Fraternity, and "the first President of the United Statss to have been coroneted an Inspector General Honorary of the Thirty-third Degree (1945)."
Masons serving in Cabinet posts under President Roosevelt were Henry Morganthau, Secretary of the Treasury; Homer Cummings and Robert H. Jackson (later a Supreme Court Justice), Attorneys- General; Daniel Roper and Jesse Jones, Secretaries of Commerce; George Dern, Secretary of War; and Claude Swanson and Frank Knox, Secretaries of Navy.
Among Masons in President Truman's Cabinet were James F. Byrnes and George C. Marshall, Secretaries of State; Tom Clark, Attorney General (and later Supreme Court Justice); Fred Vinson, Secretary of Treasury (and later Chief Justice); Louis Johnson, Secretary of Defense; Clinton Anderson, Secretary of Agriculture; and Henry Wallace, Secrtary of Commerce. Mr. Wallace also served as Vice President during Franklin D. Roosevelt's third term.
During World War II, under both Presidents Roosevelt and Truman the Chairman of the Joint Chiefs of Staff, General George C. Marshall; the Commander of the U.S. Fleet, Admiral Ernest King; and the Chief of the U.S. Army Air Corps, General Henry H. Arnold-were all members of the Masonic Fraternity.