https://en.wikipedia.org/wiki/O%27Hare_International_Airport#History

History[edit]

O'Hare was constructed in 1942–43 as part of a manufacturing plant for Douglas C-54s during World War II.[16] The site was chosen for its proximity to the city and transportation.[16] The two million square foot (180,000 m²) factory needed easy access to the workforce of the nation's then-second-largest city, as well as its extensive railroad infrastructure. Orchard Place was a small nearby farming community.[16]
Douglas Company's contract ended in 1945 and though plans were proposed to build commercial aircraft, the company ultimately chose to concentrate production on the west coast. With the departure of Douglas, the airfield took the name of Orchard Field Airport, the source of its three-letter IATA code ORD.

In 1945, Orchard Field was chosen by the city of Chicago as the site for a facility to meet future aviation demands. Matthew Laflin Rockwell (1915–1988) was the director of planning for the U.S. Army Corps of Engineers and responsible for the site selection and design. He was the great grandson of Matthew Laflin, a founder and pioneer of Chicago.
In 1949, the airport was renamed "O'Hare International Airport" to honor Edward O'Hare, the U.S. Navy's first flying ace and Medal of Honor recipient in World War II. Its IATA code, "ORD", remained unchanged, however, resulting in O'Hare being one of the rare[citation needed] instances of an airport's three-letter designation bearing no connection to the airport name or metropolitan area (with other rare instances including Orlando International Airport's IATA code "MCO" or Toronto Pearson International Airport's code of "YYZ&quot .