Presidency of Lyndon B. Johnson

Lyndon B. Johnson's tenure as the 36th president of the United States began on November 22, 1963, upon the assassination of President John F. Kennedy, and ended on January 20, 1969. He had been vice president for 1,036 days when he succeeded to the presidency.

Source: Wikipedia — Presidency of Lyndon B. Johnson (CC BY-SA 4.0)