The significant event in 1963 involving the assassination of a U.S. president was the assassination of John F. Kennedy. On November 22, 1963, Kennedy was shot in Dallas, Texas, during a motorcade. His assassination shocked the nation and the world, leading to widespread mourning and conspiracy theories. The event also triggered a change in the political landscape of the U.S., affecting policies related to civil rights and the Vietnam War. Vice President Lyndon B. Johnson was sworn in as president on the same day, further intensifying the impact of the incident on American history.