5 September 1971 is when Chicago Marathon was founded  . The official site of Chicago Marathon is www.hardrock100.com . 24 (from 5 confederations) were the number of teams who competed in Chicago Marathon . 28 from 21 nations competed in Chicago Marathon . 12 events were there in Chicago Marathon . It was held in 1 August . The venue for Chicago Marathon was  Société Athlétique de la Villa Primrose in Bordeaux (1909)
Chicago Marathon was started on 1977