If it wasn't for Jackie Robinson, it's unclear how many African-American athletes would be in pro sports today. The former multi-sport star at UCLA broke the color barrier in 1947 when he made his major league debut with the Brooklyn Dodgers. There were mixed emotions on that day, but Jackie ended up being the biggest winner of all when it was over. Since his death in 1972, MLB has picked one day out of the regular season where every play on each team were's old number 42, in honor of the late baseball and American sports hero.