A history not many people know about. From the video info:

When one researches the VERY FIRST Kentucky Derby, one will find that 13 of the 15 jockeys in the race were BLACK! Furthermore, of the first 28 Derby winners, 15 of them were black men. Going back to that first KENTUCKY DERBY, held on May 17, 1875, the winner was a 19 year-old black native of Kentucky named Oliver Lewis. It was reported that mobs of white spectators cheered for Lewis as he rode his horse, ARISTIDES to a record setting victory. In 1877, a 17 year-old black young man by the name of William Walker won the prestigious race at Churchill Downs. Quite frankly, blacks dominated the sport of horse racing in the early years. An African-American by the name Isaac Murphy was the first jockey to win 3 KENTUCKY DERBYS in 1884, 1890, and 1891. In fact, he won an unprecedented 44% of all of his races. (Thats unheard of!) Many black jockeys were introduced to horse racing at a young age partly because their light weight virtually made the horse feel that it wasnt carrying a load. So it is of no surprise that the black jockey named James Soup Perkins, who won the Derby in 1895, began racing at age 11. The youngest black jockey to ever win at Churchill Downs was Alonzo Lonnie Clayton who rode to victory at age 15 in 1892. By the year 1921, racism and bigotry in America eventually drove the black jockeys out of the sport. White racing fans that grew increasingly in frustration at the vast number of black Derby winners, began to voice their disapproval of their involvement by refusing to attend the races, let alone place bets. When the black jockeys disappeared from Churchill Downs, the white racing fans responded by filling the seats once again to cheer on horses ridden by white men. When Marlon St. Julien raced in the year 2000 Kentucky Derby, he broke the 79 year-old hiatus of the black jockey from Churchill Downs.