How many presidents were in the 1940s?

In the 1940s, there were two U.S. presidents: Franklin D. Roosevelt and Harry S. Truman. Franklin D. Roosevelt served until his death in April 1945, after which Harry S. Truman, who was his vice president, assumed the presidency. Truman served for the remainder of the decade, completing the term and then winning a full term in the 1948 election.