From Amtrak Union Station to Midway Airport
All Amtrak trains serving Chicago arrive at Union Station. The best way to travel between the Amtrak station and the airport is by the CTA rail. Trains are fast and run frequently, and the entire journey (including all waiting and walking) takes approximately 1 hour. Beware that private shuttles run much less frequently than the CTA trains do (about once an hour compared to every 5-10 minutes), and so on average you are not going to save much time by taking a shuttle despite paying at least 10 times as much as the cost of a train ride. Moreover, trains run until later at night, and trains do not risk getting stuck in Chicago traffic. Unless you have a lot of heavy luggage, a train ride is a more sensible option in most cases. The two maps you will need for this journey are the Downtown Chicago map and the CTA rail map.
First of all, you need to get to the CTA station (Quincy station on the Orange line). Quincy station is located three blocks (400 m) east of Union Station (map). Exit Union Station to Adams or Jackson and walk east across Chicago river towards Sears Tower. The entrance to the CTA station is located between Adams and Jackson underneath the elevated structure crossing both streets (trains run on that elevated structure). The entire walk takes about 5 minutes.
Now you are at the CTA station. The fare is $2.25. Buy a transit card from the farecard machines (cash only). Exact fare is required; however, one transit card can be shared by several people - just put enough money for all the riders. Pay your fare, pass through the turnstiles to the boarding platform marked "Orange line", and board any Orange line train. Beware that Pink line trains also stop at the same platform, so check the color destination signs on the arriving train to make sure you are taking a correct one. Travel to Midway station and get off the train. Travel time from Quincy to Midway is 33 minutes; trains run every 10 minutes daily.
Finally, you need to get from the CTA station to the terminal. Take the pedestrian overpass to the parking building, pass through the building, and follow the signs to the terminal. The entire walk takes about 10 minutes.
The total travel time from Union Station to Midway should be about an hour including all walking, waiting and riding the train. So, it is safe to have 1 hour 5 minutes to make this connection between the Amtrak station and the airport.
The last Orange line train leaves Quincy at 01:25 on weekdays and Saturdays and at 23:55 on Sundays and holidays.
If you still have any questions, feel free to email me (no phone calls please).