From O'Hare Airport to Chicago Union Station
All Amtrak trains serving Chicago depart from Union Station. The best way to travel between the airport and Union Station is by the CTA rail. Trains are fast and run frequently, and the entire journey (including all waiting and walking) takes approximately 1 hour 15 minutes. Beware that private shuttles run much less frequently than CTA trains do (about once an hour compared to every 10 minutes), and so on average you are not going to save much time by taking a shuttle despite paying at least 5 times as much as the train fare. Moreover, trains run at all times, 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 CTA rail map and the Downtown Chicago map.
First of all, you need to get to the CTA station (the O'Hare station on the Blue line). If your flight arrived at any of the domestic terminals (Terminal 1, 2 or 3), just follow the signs "Trains to City" from any terminal. The walk from any gate to the station takes about 10 minutes. If your flight arrived at the International terminal (Terminal 5), you will need to take the Airport Transit System (ATS) first. Follow the signs "Trains to City" or "Airport Transit System" and get to the ATS station. Take an automated train to Terminal 3, get off, take an escalator up, turn left, walk to the elevators in the parking building, take an elevator down to the "CTA" level, and follow the underpass to the CTA station. The entire trip takes about 15 minutes.
Now you are at the CTA station. The fare is $5. Buy a single-ride ticket from the farecard machines (cash, debit or credit cards). Pay your fare and pass through the turnstiles to the boarding platform. Take any train and travel to the Clinton station on the same Blue line. The travel time from O'Hare to Clinton is 46 minutes; trains run every 5-10 minutes daily.
Finally, you need to get from the CTA station to Union Station. Union Station is located two blocks (300 m) north of the Clinton station (map). Take the escalator up and simply walk north along Clinton (there is a sign pointing in the direction of Union Station at the exit from the Clinton station). You will see an entrance to Union Station near the intersection with Jackson (there is also an accessible ramp down into the station on its Clinton side just after the taxi drive-in entrance). The entire walk takes about 5 minutes.
The total travel time from O'Hare to Union Station should be about 1 hour 15 minutes including all walking, waiting, and riding the train (about 1 hour 20 minutes if you are coming from the International terminal).
The Blue line operates at all times, and so there is no last train to miss.
If you have any questions, please check the "Frequently Asked Questions" page first. If you carefully read all of the above, checked the FAQs, and still have a question, please feel free to contact me.
Reverse directions: from Chicago Union Station to O'Hare Airport