Jackie Robinson | 42 | Montreal | Dodgers
Jackie Robinson broke the Major League Baseball color barrier in 1947, had a 10-year all-star career, became the first African-American inducted into the Baseball Hall of Fame, and had his number 42 retired by Major League Baseball in 1997. More important than his accomplishments in baseball are his contributions to racial equality in the United States, of which his many baseball “firsts” are just one part. After his retirement from baseball in 1956, he became very active in the civil rights movement, working with the National Association for the Advancement of Colored People (NAACP) and on several political campaigns to help break barriers for all people, not just athletes.
Source: https://postalmuseum.si.edu/exhibition/the-black-experience-sports-baseball/jackie-robinson