Ansel Williamson was born a slave in Virginia sometime around the middle part of the 19th century. In 1864 he was purchased by Robert A. Alexander, owner of the famous Woodburn Stud near Midway, Kentucky. Taught the breeding and training of horses, after he was freed Williamson remained in Alexander's employ. He conditioned a number of successful horses including the undefeated U.S. champion three-year-old male, Norfolk and the undefeated Asteroid.
Following Robert Alexander's death in 1867, Williamsom went on to train many great horses including Tom Bowling, who won 14 of his 17 races, and Virgil who was the sire of the great Hindoo. However, he is best remembered for having trained Aristides, the winner of the inaugural Kentucky Derby in 1875. That same year, his horse Calvin won the Belmont Stakes. In addition, Williamson trained horses who won other major races such as the Travers Stakes, the Jerome Handicap, and the Withers Stakes.
Following its formation, in 1998 Ansel Williamson was inducted posthumously into the National Museum of Racing and Hall of Fame.