According to F. Scott Fitzgerald, "There are no second acts in American life". Apparently, he never met Chicago's Midway Airport. Of course, this is literally true, since at the time of the famous author's death, in December 1940, the airport still bore its original name: The Chicago Municipal Airport. The current appellation wouldn't be applied (for the battle of Midway during World War II) until the late 1940s, so Fitzgerald can certainly be forgiven for not imagining what might take place in the future.
Following the opening of O'Hare Field on Chicago's far-northwestern side, commercial air service in the "Windy City" migrated almost exclusively to the newer facility, leaving MDW virtually bereft of scheduled airline service during the latter part of the 1960s. The advent of smaller jet aircraft such as the 727, 737 and DC-9 that were able to utilize the southside airport's relatively short runways, coupled with renovation and expansion of the terminal facilities brought back some service during the late 1960s, and carriers such as Mohawk, Northeast, Piedmont and Southern, which had not been serving the Chicago market, gained entry by flying to Midway instead of ORD, along with a modicum of services by the larger trunks, including American, Delta, TWA and United. UA's headquarters had been located across Cicero Avenue from the terminal prior to the carrier departing for the suburbs near O'Hare earlier in the decade.
Following "Deregulation" in the U.S. in 1978, the very first 'new entrant' carrier certified was Midway airlines, which began operating in 1979 specifically to serve the older Chicago airport. In a further display of solidarity with its airfield home, the new airline selected the former United headquarters as its executive suite, as well. Other carriers followed, including Southwest in the mid-1980s, aided by the fact that Midway had capacity that could be utilized to enter the large Chicago market, while slot restrictions at O'Hare effectively precluded a non-incumbent carrier from establishing a significant presence there.
In 1991, however, Midway Airlines declared bankruptcy, and left the scene, with Southwest taking over much of the failed carrier's facilities in the process. Two years later there was a significant improvement in ground access, when the Orange Line of the Chicago Transit Authority began providing service between MDW and downtown Chicago.
In 1993, a second iteration of Midway Airlines appeared, and began operations at the airport using Fokker 100s. While the name was retained, Midway (II) quickly decamped to North Carolina, and developed a hub at the Raleigh-Durham airport, following the departure of the American Airlines hub that had operated there previously.
Later, American Trans Air, which had started as an Indianapolis, Indiana-based travel club, with a single aircraft, established a 'focus city' operation at Chicago-Midway. This expanded considerably, and including an associated commuter feeder carrier, Chicago Express/ATA Connection. However, the carrier filed for bankruptcy in 2004, and eventually failed, in 2008, leaving Southwest and AirTran as the dominant operators.
Interestingly, MDW now functions much as it did in its 1950s-heyday, prior to the opening of O'Hare, providing nonstop service to most important cities for local Chicago traffic, as well as a convenient connecting point for passengers traveling across the U.S. During several visits in 2012, this was emphasized visually by the numerous signs individually listing the roll call of major destinations emanating from the airport. Of course there is a significant difference now: in the 1950s, many passengers transferred from one carrier to another at Midway, carrying on the tradition of the era when passenger railroads were ascendant; now, most connecting passengers arrive and depart on the same carrier-Southwest.