Lyndon B. Johnson was the president of the United States after John F. Kennedy was assassinated. Johnson became the 36th president on November 22, 1963.
Prior to becoming president, Johnson was Kennedy's running mate, then became the Vice President of the United States in 1961. He was sworn in as President because of Kennedy's demise. However, in the presidential elections of 1964, he was victorious with 61 percent of the vote. Under his leadership, the U.S. achieved several notable milestones. One of the greatest was the advancement in the exploration of space when three astronauts were sent to the moon in 1968.