Truman's middle initial
Truman did not have a middle name, but only a middle initial. It was a common practice in southern states, including Missouri, to use initials rather than names. Truman said the initial was a compromise between the names of his grandfathers, Anderson Shipp(e) Truman and Solomon Young. He once joked that the S was a name, not an initial, and it should not have a period, but official documents and his presidential library all use a period. Furthermore, the Harry S. Truman Library has numerous examples of the signature written at various times throughout Truman's lifetime where his own use of a period after the 'S' is very obvious."
- from the article on Harry S. Truman at Wikipedia, the free encyclopedia