The first full year of auto racing at the Indianapolis Motor Speedway was 1910. Races were held over the weekends of Memorial Day (then called Decoration Day), the Fourth of July, and Labor Day. However, attendance fell off over the summer. The speedway’s management felt there had been too much racing, and the decision was made to do just one long race in 1911.
The Fourth of July was considered, but Decoration Day was chosen for several reasons. The Decoration Day races had been the most successful of the 1910 season. Local farmers typically took a break in late May after “haying” (baling hay). Decoration Day was then a fixed holiday occurring on May 30. Because many people worked on Saturday, the first Indianapolis 500 was held on Decoration Day itself, which occurred on a Tuesday in 1911.
Five hundred miles was chosen as the distance for the race because, based on the speed of racing automobiles in 1911, such a race could begin at 10 AM and finish in time for spectators to return home for supper.
Memorial Day was moved to the last Monday in May in 1971. That year and the next the Indianapolis 500 was held on Saturday, and in 1973 a major accident and rain postponed the race from Monday until Wednesday. Since 1974 the Indy 500 has been scheduled for the Sunday of Memorial Day weekend. Because of the outbreak of the COVID-19 pandemic in early 2020, the 104th Indy 500 was held later that year on August 23.