Monday 31st May 1915
Ralph DePalma driving a Mercedes 18/100 accompanied by riding mechanic Louis Fontaine won the Indianapolis 500. The traditional race date of May 30 fell on a Sunday, but race organizers declined to schedule the race for Sunday. The race was set for Saturday May 29, but heavy rains in the days leading up to the race flooded the grounds and made some roads leading to the track impassible. Officials decided to postpone the race until Monday May 31 in order to allow the grounds to dry out. Speedway management would maintain their policy to not race on Sundays until 1974.