Yeah, Milwaukee is close enough to Chicago that travel times for Milwaukee-originating passengers wouldn't be horrible, using that schedule. North/west-bound, it essentially provides a midnight train to St. Paul. South/east-bound, it provides an early-morning train to Chicago, potentially opening up connections to morning trains from Chicago that are otherwise unavailable.Looking at the 1978 timetable for the Chicago-Duluth North Star, #9 left Chicago at 10:30 p.m., left Milwaukee at 12:05 a.m., and arrived in St. Paul at 7:15 a.m. #10 left St. Paul at 10:15 p.m., arrived in Milwaukee at 5:35 a.m., and arrived in Chicago at 7:10 a.m. That predates me so I'm not sure how well it kept to that timetable.
I've always been curious about the idea of a Chicago-based overnight train network. It seems easy enough to sort out Chicago departure times, as there should be plenty of platform availability in the 10pm-midnight timeframe. But I've never quite figured out the best approach to take for Chicago arrival times, as platform availability is much scarcer in the morning rush period.