The i.O. Theatre in Chicago

Detail: Founded in 1981 by Charna Halpern, with assistance from the late Del Close starting in '84, the i.O. Theater has prospered as a comedy training center and performance venueLocated across the street from Wrigley Field, i.O. is renowned for the performing and teaching of long-form improvisational theater (including the house specialty, the Harold). i.O.'s Los Angeles counterpart, i.O. West, recently celebrated its fifth anniversary and has been performing in a new theater since October 2001.