Truman was very involved with the Freemasons. In fact, the 33rd president helped found a Masonic Lodge in Belton, Missouri in 1911 and was elected its first master, according to the Truman Library.
The young Missourian was immediately hooked on Freemasonry. The Truman Library also cites some of Truman's letters to his future wife Bess Wallace, during which he confessed to having "the big head terribly" and warned her that he'd forever "... be bragging about having performed that ceremony."
Apparently, Truman's lodge hall burned down while he was serving in WWI, but he continued to rise within the Freemasons throughout the 1920s.
The Truman Library cited one observer's assessment of Truman's leadership abilities in the society: "… He did a good job in the lodge work. Excellent. He was an excellent director. If things weren't going right along smoothly, Harry would come in and get them to going. He was a good lodge man."
He eventually became a grand master mason, but ended his role in a "blaze of glory" the next year, while still a US senator.
A few years later, during his presidency, he remained a committed Mason. The New York Times reported that Truman's "only jewelry was a double-band gold Masonic ring on the little finger of his left hand." The Truman Library also reports that in 1945 Truman became the only president to received the 33rd degree of the Supreme Council of the Scottish Rite.
In "Harry S. Truman: His Life and Times," Brian Burnes quotes Truman as writing: "Freemasonry is a system of morals which makes it easier to live with your fellow man, whether he understands it or not."
Source : http://www.businessinsider.com/us-presidents-who-were-masons-2017-3