At the first Indianapolis 500 in 1911, his use of what would now be called a rear-view mirror, rather than the riding mechanic specified in the rules, created controversy, but was ultimately allowed. Harroun went on to win at an average speed of . Harroun, who came out of retirement to race in the first 500, would not race after 1911. Harroun's historic Firestone-shod yellow #32 Marmon "Wasp," in which he won the Indianapolis 500, is on display at the Indianapolis Motor Speedway Hall of Fame Museum.