Question: what was the last horse to win triple crown
Answer: Only twelve horses have won the Triple Crown : Sir Barton ( 1919 ) , Gallant Fox ( 1930 ) , Omaha ( 1935 ) , War Admiral ( 1937 ) , Whirlaway ( 1941 ) , Count Fleet ( 1943 ) , Assault ( 1946 ) , Citation ( 1948 ) , Secretariat ( 1973 ) , Seattle Slew ( 1977 ) , Affirmed ( 1978 ) , and American Pharoah ( 2015 ) .