 Jack was only 12 years old when he rode his first winner on a small track in Lemmon, South Dakota.By age 15, while still officially an apprentice jockey, he was the leading rider in the U.S. for 1933.Westrope scored 301 victories from the 1,224 races he competed in that year, giving him a 25% win rate, the highest for any national title holder during the past twenty-four years.