12 events were there in Chicago Marathon . Chicago Marathon was established on 5 September 1971 . 28 from 21 nations were the competitors in Chicago Marathon . 1 August was when it was held . 24 (from 5 confederations) were the number of teams who competed in Chicago Marathon . The venue for Chicago Marathon was  Société Athlétique de la Villa Primrose in Bordeaux (1909) . The sport has the official site www.hardrock100.com
Chicago Marathon was held over a few days