Original: 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.
Simplified: 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.