From O'Hare Airport to Midway Airport
The best way to travel between the two airports is by the CTA rail. Trains are fast and run frequently, and the entire journey (including all waiting and walking) takes approximately 1 hour 55 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 until late 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 only map you will need for this journey is the CTA rail 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 Clark station on the same Blue line. The travel time from O'Hare to Clark is 39 minutes; trains run every 5-10 minutes daily.
At Clark you will have to transfer from the Blue line to the Orange line. Follow the signs "To Orange line" and take the escalators all the way up to connect from the subway station to the elevated one. The transfer between the lines is free (unless you exit through the turnstiles, which you certainly should not do). On the platform of the elevated station board any Orange line train. Beware that several other CTA lines also serve the same platform, so check the color destination signs on the arriving train to make sure you are taking the correct line. Travel to the Midway station and get off the train. The travel time from Clark to Midway is 28 minutes; trains run every 8-12 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 O'Hare to Midway should be about 1 hour 55 minutes including all walking, waiting, and riding the trains (about 2 hours if you are coming from the International terminal).
While the Blue line operates at all times, the Orange line does not. The last Orange line train leaves Clark at 01:30 daily. In order to catch the last Orange line train you will have to leave O'Hare no later than 00:45 daily.
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 Midway Airport to O'Hare Airport