
It’s now lost to time why Harry Truman’s parents decided on just an “S” for their son’s middle name. Perhaps it was because they couldn’t agree which of their fathers was most deserving of the naming tradition, and so instead, they decided to make it simply an “S,” honoring both. It’s likely that we’ll never know for sure. Since it’s just “S” and there’s no actual name in the middle explains why Harry S. Truman is sometimes punctuated as Harry S Truman, without a period.
Publishing editors being who they are, however, means that a missing period caused much consternation and debate shortly after Truman was elected to office. Per Truman Library, several popular style manuals insist on the period, including the U.S. Government Printing Office Style Manual and the Chicago Manual of Style. There’s evidence, however, that Truman himself went back and forth on the matter, but in 1962, he did confirm that in his view, the period was not required.