Jackie Robinson's primary contribution to American history is leading the integration of Major League Baseball when he joined the Brooklyn Dodgers in 1947.
He started his career as a second baseman with the Negro Leagues team the Kansas City Monarchs. He was then approached by the Brooklyn Dodgers' general manager, Branch Rickey, who wanted to integrate baseball. Robinson was eased into the Majors, starting with the Montreal Royals, "the Dodgers' top farm team," in 1946 and securing his promotion to the Dodgers by establishing a leading record with the International League.
Robinson was unwanted initially by both audiences and his teammates. However, he was passionate about civil rights—while in the army, he was court-martialed for refusing to move to the back of a bus—and knew that his unique position would pave the way for other black players and it did.
Later in life, Robinson became active in politics. Unlike many black people at the time, he was a registered Republican and campaigned for Richard Nixon in 1960. He was disappointed, however, by Nixon's lack of commitment to civil rights.