Chicago Midway International Airport traces its origins to 1923, when a 320-acre plot on Chicago's Southwest Side was first used as Chicago Air Park, primarily for airmail. The city leased the field for commercial operations in 1926, and on May 8 of that year the first commercial flight departed, a National Air Transport plane bound for a mail route stretching to Dallas. The airport was formally dedicated as Chicago Municipal Airport on December 12, 1927. By 1928, it had 12 hangars and 4 runways lit for night operations.

Growth was rapid. By 1932, the airport was the world's busiest, a distinction it held, with brief interruption, until 1961. At its peak in 1959, the airport processed 10 million passengers on a single square mile of land, a footprint defined by surrounding residential development that has never materially changed. The name Midway was adopted in 1949 to honor the World War II naval battle in the Pacific. When O'Hare opened to airlines in 1955 and the jet age required longer runways than MDW could provide, the major carriers departed, and by mid-1962 the airport had nearly gone quiet. Midway Airlines, founded in 1976 as one of the first post-deregulation carriers, revived operations and gave the airport new life.

Today, MDW is a major base for Southwest Airlines, accounting for over 90% of the airport's passenger traffic. The current terminal complex, completed in 2001, bridges Cicero Avenue and connects 3 concourses and 43 gates in a compact, walkable layout. The CTA Orange Line, which opened to the airport in 1993, links MDW to the downtown Loop in roughly 25 minutes. In 2023, the airport handled more than 22 million passengers, all of it on that same historic square mile.