Lyndon B Johnson, often referred to by his initials LBJ, was an American politician who served as the 36th president of the United States from 1963 to 1969. He became president after the assassination of John F. Kennedy, under whom he had served as the 37th vice president from 1961 to 1963. A Democrat from Texas, Johnson also served as a U.S. representative and U.S. senator.