Horse racing in the United States Horses and inspired their name. With the exception of the longer, distance contests, Quarter Horse races are run flat out, with the horses running at top speed for the duration. There is less jockeying for position, as turns are rare, and many races end with several contestants grouped together at the wire. The track surface is similar to that of Thoroughbred racing and usually consists of dirt. The traditional high point of US horse racing is the Kentucky Derby, held on the first Saturday of May at Churchill Downs in Louisville, Kentucky. Together, the Derby; the Preakness Stakes, held two
American Quarter Horse hence the nickname. Horses listed in the appendix may be entered in competition, but offspring are not initially eligible for full AQHA registration. If the Appendix horse meets certain conformational criteria and is shown or raced successfully in sanctioned AQHA events, the horse can earn its way from the appendix into the permanent studbook, making its offspring eligible for AQHA registration. Since Quarter Horse/Thoroughbred crosses continue to enter the official registry of the American Quarter Horse breed, this creates a continual gene flow from the Thoroughbred breed into the American Quarter Horse breed, which has altered many of the characteristics