Mollie McCarty vs Ten Broeck (horse race)
On July 4, 1878, one of the greatest horse races of all times took place in Louisville, KY, when African American jockey William "Billy" Walker, Sr., riding Ten Broeck, defeated the western racehorse champion, Mollie McCarty.
Thoroughbred mare Mollie McCarty [or McCarthy], owned by Theodore Winters, was undefeated prior to the July 4th race in Louisville and was also thought to be the first California-bred horse to travel east to compete in a race. She was carried by a special train from California to Louisville, arriving early to prepare for the race.
Ten Broeck was the eastern champion, owned by Frank B. Harper from Lexington. The horses ran four mile heats at Churchill Downs on a muddy track for the sum of $10,000 (some sources say $20,000). The arrangements were made by the Louisville Jockey Club. The race is said to be the last of the great races for long-distance contests.
There are several songs memorializing the race, including Mollie and Tenbrooks by The Del McCoury Band with Vince Gill on vocals [available on YouTube].
For more, see "Ten Broeck" in The Horse-breeder's Guide and Hand Book, p. 156, by S. D. Bruce; and The American Thoroughbred, by C. E. Trevathan [both available full-text at Google Books].