Chicago Marathon was established on 5 September 1971 . 28 from 21 nations were the competitors in Chicago Marathon . 24 (from 5 confederations) were the number of teams who competed in Chicago Marathon . The sport has the official site www.hardrock100.com .  Société Athlétique de la Villa Primrose in Bordeaux (1909) were the venues of Chicago Marathon . The no. of events in sport was 12 . 1 August was when it was held
Chicago Marathon was a single day event