On this day in 1945, U.S. President Franklin D. Roosevelt died while in office; Vice President Harry Truman became President upon Roosevelt's death.
On this day in 1955, the polio vaccine, developed by Dr. Jonas Salk, was declared safe and effective.
On this day in 1999, US President Bill Clinton was cited for contempt of court for giving "intentionally false statements" in a sexual harassment civil lawsuit.