U.S. History Timeline By Deerfieldn Apr 1, 1945 Truman becomes president Aug 6, 1945 Atomic bombs dropped on Hiroshima and Nagasaki Jan 1, 1946 Cold War begins between U.S. and Soviet Union Jan 1, 1947 Truman Doctrine Jan 1, 1949 NATO Treaty Jan 1, 1950 Korean Conflict Jan 1, 1953 Presidency of Truman ends Jan 1, 1958 NASA formed Jan 1, 1959 Cuban revolution Jan 1, 1960 Greensboro Sit-in Jan 1, 1961 Vietnam war begins Jan 1, 1962 Cuban missile crisis Jan 1, 1963 President Kennedy assassinated Nov 22, 1963 Johnson elected president Jan 1, 1964 Civil Rights Act Jan 1, 1968 Presidential candidate Robert Kennedy is assassinated Jan 20, 1969 Nixon elected president Jan 20, 1969 Johnson's presidency ends Jul 20, 1969 Neil Armstrong walks on the moon Jun 17, 1972 Watergate Scandal Aug 9, 1974 Nixon resigns