One of the key sporting events of each spring is the Kentucky Derby, and tomorrow’s running will be the 139th in the race’s long history. The first event was held in 1875, won by a horse named Aristides. Patterned after the English Derby, the race was a mile and a half long until shortened to a mile and a quarter in 1896, where it remains. Some of the famous horses to win the Run for the Roses include War Admiral, Whirlaway, and Secretariat. Last year’s winner was I’ll Have Another. At tracks across the U.S., less famous thoroughbred and harness racing draws more than 6.5 million spectators a year, and race animal training is a $680 million a year business. Profile America is in its 17th year as a public service of the U.S. Census Bureau.