ess . ▁ ▁The ▁character ▁of ▁the ▁I RS ▁agent ▁Oscar ▁Wal lace ▁was ▁based ▁on ▁Frank ▁J . ▁Wilson , ▁the ▁I RS ▁criminal ▁investig ator ▁who ▁spent ▁years ▁keeping ▁tabs ▁on ▁Cap one ' s ▁financial ▁deal ings ▁before ▁lay ing ▁charges . ▁ ▁In ▁prepar ing ▁for ▁his ▁role ▁as ▁Eli ot ▁N ess , ▁Kevin ▁Cost ner ▁met ▁with ▁former ▁F BI ▁agent ▁and ▁U nt ouch able ▁Al ▁" W all paper " ▁Wol ff ▁at ▁his ▁home ▁in ▁Lincoln wood , ▁IL ▁for ▁historical ▁context ▁and ▁to ▁learn ▁about ▁N ess ' s ▁manner isms . ▁ ▁Production ▁Princi pal ▁phot ography ▁began ▁in ▁the ▁summer ▁of ▁ 1 9 8 6 ▁in ▁Chicago , ▁Illinois , ▁where ▁Eli ot ▁N ess ' s ▁story ▁begins ▁with ▁him ▁rec ruit ing ▁his ▁U nt ouch ables ▁team ▁with ▁the ▁intent ▁of ▁taking ▁down ▁Al ▁Cap one . ▁In ▁August ▁ 1 9 8 6 , ▁Param ount ▁Pictures ▁contact ed ▁Gar ry ▁W under wald ▁of ▁the ▁Mont ana ▁Film ▁Commission er ' s ▁Office ▁to ▁find ▁a ▁ 1 9 3 0 - period ▁bridge ▁to ▁imply ▁a ▁border ▁crossing ▁between ▁the ▁United ▁States ▁& ▁Canada . ▁W under wald ▁suggested ▁the ▁Hard y ▁Bridge , ▁which ▁cross es ▁the ▁Missouri ▁River ▁near ▁the ▁small ▁town ▁of ▁Cas cade , ▁south west ▁of ▁Great ▁F alls . ▁ ▁From ▁ ▁the ▁bridge ▁was ▁closed ▁to ▁traffic ▁to ▁film ▁the ▁icon ic ▁shoot out ▁sequence . ▁Tw