1 August was when it was held . 24 (from 5 confederations) teams participated in Chicago Marathon . 28 from 21 nations were the competitors in Chicago Marathon . The official site of Chicago Marathon is www.hardrock100.com .  Société Athlétique de la Villa Primrose in Bordeaux (1909) were the venues of Chicago Marathon . 5 September 1971 is when Chicago Marathon was founded  . 12 events were there in Chicago Marathon
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