Trading spaces: CME moves The Great Migration of Chicago traders is almost over and that means a new era begins for the Chicago Mercantile Exchange. Today is the final day of trading at the old Merc, its home for nearly 25 years at 20 S. Wacker. It will be left to the meat traders, stalwarts whose business goes back to the exchange's earliest days, to turn out the lights for good. They will mark the occasion with laughter and lumps in their throat and maybe smuggle in a flask or two to give the place a proper sendoff.