Chicago Midway International Airport is a major commercial airport on the southwest side of Chicago, Illinois. It was the city's primary airport from the time it opened in 1927 until 1955, when O'Hare International Airport was opened roughly 20 miles (32 km) to its north. Located on one square mile (2.59 sq. km), Midway remains the second-busiest airport in the state of Illinois, having served 22 million passengers in 2018.