As we celebrate Martin Luther King Jr. Day, take a look back at the pioneering African-Americans who changed the way their sport was played.

Jackie Robinson breaking major league baseball's color barrier is undoubtedly one of the watershed moments in sports, and American history. Robinson made his major-league debut with the Brooklyn Dodgers in 1947, bringing an end to segregation in baseball. In 1997, 50 years after Robinson's debut, the MLB retired his jersey number 42 league-wide in recognition of his impact as a player.

In 1970, outfielder Curt Flood legally challenged Major League Baseball's reserve clause. The Supreme Court ruled against him, but his bravery later helped bring free agency to baseball.

Were you ever so good at something that the rules were changed to stop you? Well, that's what happened to Wilt Chamberlain. Some of the changes were the widening of lanes and adding offensive goaltending. Despite all that, he still dominated in the NBA.

Billy "White Shoes" Johnson made three Pro Bowls as a wide receiver/returner, but he's more known for popularizing the touchdown dance and the celebrations haven't stopped.

The alley-oop is a common play in modern basketball, but David Thompson popularized it in the 1970s. What's even more remarkable is that Thompson is not even 6-foot-5.

Nobody had really heard of a 6-foot-9 point guard before Magic Johnson. He paved the way for the universal player -- the guy who can play any position on the floor. Just ask Sixers fans how Magic was as a center in the 1980 Finals.

Jim Brown helped redefine the running back position when he was tearing through defenses as a member of the Cleveland Browns from 1957-65. He was as big as linebackers and nobody could catch him in the open field. Players such as Bo Jackson and Adrian Peterson have to look at Brown as the prototype for running backs with the perfect blend of strength and speed.

Tiger Woods' 12-stroke win in The Masters signaled a new era in golf. Executives around the country were "Tiger-proofing" their courses to try to stop the phenom.
 

"Bo Knows" was a huge phrase in the 1980s. Bo Jackson was a force on the gridiron and also starred on the baseball diamond. He opened the door for Deion Sanders to do the same thing later on.

Carl Lewis changed track and field forever. It wasn't just that he won nine Olympic gold medals. Lewis helped make races more lucrative, which in turn helped keep top athletes in the sport.