Originally Posted by diburning

Just so you are aware, the CTA L metro does not get you to Union Station. You would have to get off and walk several blocks. However, if you catch the last train in time, the commuter railway will take you to Union Station. You can get the METRA train behind the Multi-Modal Facility (last stop on the ATS people mover, one stop away from Terminal 5) Be sure to check the schedule. The current schedule has departures at 6:17AM, 6:58AM, 7:59AM, 8:59AM, 10:09AM, and 4:36PM. Download the METRA app to buy a ticket. It costs more than the metro, but it's a slightly faster and slightly more pleasant ride.