In 2003 , the Firestone Indy Lights Series , a minor league series of the Indy Racing League , started racing at the Speedway . They were the first series to race in May other than the 500 since 1910 . In 2003 , the Firestone Indy Lights Series , a minor league series to the IndyCar Series , made history with the first May race at the track since 1910 , other than the 500 .