Since the American League joined the National League as a baseball major league in 1901, the batting triple crown — leading a league in batting average, home runs and RBIs — has been achieved 15 times, 10 in the AL and five in the NL. But only five players won the MLB triple crown leading both leagues in all three categories.
Not surprisingly, it's five of the all-time greats.
1909 – Ty Cobb of the Tigers batted .377 with nine home runs and 107 RBIs. If the homers total sounds low, that was the dead ball era when homers were few and far between.
1925 – Roger Hornsby of the Cardinals – .403/39/143.
1934 – Lou Gehrig of the Yankees – .363/49/166.
1942 – Ted Williams of the Red Sox – .356/36/137.
1956 – Mickey Mantle of the Yankees – .353/52/130.
For four of the five, the triple crown year was not their best season.
Cobb's best year was 1911 with career highs for average (.419) and RBIs (127). With eight homers he fell one short of a second AL triple crown.
Hornsby's best season with 1922 when he won the NL triple crown with a .401 average, career highs in homers with 42 and RBIs with 152 and a National League record 450 total bases.
Gehrig's best year was 1927 – .373/47/175.
Williams' two best seasons were 1941, the year he hit .406, and 1949 when he had career highs with 43 homers and 159 RBIs, but missed a third AL triple crown in history's closest batting race with a .3426 average to .3429 for the Tigers' George Kell. Both officially batted .343.
1956 was Mantle's best season.
Gehrig and Williams did not win AL MVP in their triple crown seasons. Despite leading the AL in most offensive categories in 1934, Gehrig finished fifth in the voting, won by player-manager Mickey Cochrane for the pennant winning Tigers. Williams was second behind Yankee second baseman Joe Gordon in 1942.
Hornsby and Mantle were MVPs in their triple crown season and there was no award in 1909.
Hornsby in the NL and Williams in the AL are the only players to win two league MVPs. Williams' second came in 1947 when he also failed to win the MVP, losing out to the Yankees' Joe DiMaggio by one point in the voting.
Jimmie Foxx would be the only MLB player with back to back league triple crowns under current rules. He won the AL triple crown in 1933 and led in homers and RBIs in 1932, but finished second to Dale Alexander of the Red Sox for the batting title, .367 to .364. Alexander did not have enough pate appearances to qualify under current rules
Baseball now recognizes stats from the Negro Leagues. Oscar Charleston won triple crowns in 1921, 1924 and 1925. The great Josh Gibson won back to back triple crowns in 1936 and '37.