From Midway Airport to O'Hare 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 10 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 Midway station on the Orange line). From the terminal just follow the signs "Trains to City". Pass through the parking building and take the pedestrian overpass to the station. The walk from any gate to the station takes about 10 minutes.
Now you are at the CTA station. The fare is $3. 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 Orange line. The travel time from Midway to Clark is 31 minutes; trains run every 8-12 minutes daily.
At Clark you will have to transfer from the Orange line to the Blue line. Follow the signs "To Blue line" and take the escalators all the way down to connect from the elevated station to the subway 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 subway station board any Blue line train headed to O'Hare (check the destination signs on the arriving train). Travel to the O'Hare station and get off the train. The travel time from Clark to O'Hare is 39 minutes; trains run every 5-10 minutes daily.
Finally, you need to get from the CTA station to your departure terminal. If your flight departs from any of the domestic terminals (Terminal 1, 2 or 3), simply follow the signs to that terminal. Upon exiting the rail station take the underpass to the right to Terminal 1, the underpass straight ahead to Terminal 2, or the underpass to the left to Terminal 3. The entire walk takes about 10 minutes. If your flight departs from the International terminal (Terminal 5), you will need to take the Airport Transit System (ATS) first. Upon exiting the rail station walk towards Terminal 3 (follow the underpass to the left), just before passing the first set of the glassy doors turn left again, follow the narrow tunnel until it ends, take an elevator up to Level 4, walk to the overpass in the parking building, take an escalator down to the ATS station, and travel by an automated train to Terminal 5. The entire trip takes about 15 minutes.
The total travel time from Midway to O'Hare should be about 1 hour 55 minutes including all walking, waiting, and riding the trains (about 2 hours if you are going to the International terminal).
While the Blue line operates at all times, the Orange line does not. The last Orange line train leaves Midway at 01:00 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 O'Hare Airport to Midway Airport