John F. Kennedy (1963)

The assassination of President John F. Kennedy on 22 November 1963 remains the most analyzed event in American history, with the Warren Commission's finding of a lone gunman disputed by 60% of Americans as of 2023. While less structurally transformative than Lincoln's assassination (#2), Kennedy's death had immediate policy consequences: Lyndon B. Johnson used national grief to pass the Civil Rights Act of 1964 and the Voting Rights Act of 1965—landmark laws Kennedy himself could not push through Congress. The 25th Amendment, clarifying presidential succession, was also ratified in 1967 as a direct result. The assassination reshaped the Secret Service's protective protocols, which now cost over $3 billion annually.