Chicago Rockford International Airport , typically referred to as Rockford International Airport, Chicago Rockford, or by its IATA call letters, RFD, is a commercial airport in Rockford, Illinois, located northwest of Chicago. Established in 1946, the airport was built on the grounds of the former Camp Grant facility, which served as one of the largest training facilities for the U.S. Army during both World Wars. The Federal Aviation Administration (FAA) National Plan of Integrated Airport Systems for 2017–2021 categorized it as a non-hub primary commercial service facility. As an alternative location for leisure-oriented travelers, the airport currently receives passenger service through Allegiant Air, which flies to six year-round destinations. The third-busiest Chicago airport in Illinois, the Rockford Airport served 103,000 passengers in 2021. RFD is among the fastest-growing cargo airports in the world. The Airport specializes in cargo operations; processing over of cargo, the airport is the 14th-busiest cargo airport in the United States. UPS Airlines operates a major hub at the airport. The airport is also served by Amazon Air. In the 2020s, cargo operations underwent further expansions, attracting cargo flights from Germany and China. History RFD traces its history to 1917, when Camp Grant was established by the U.S. Army as one of the largest military training facilities in the United States. At the end of 1923, the Army closed Camp Grant as an active facility, transferring it to the Illinois National Guard. In 1941, the facility was reactivated by the Army. During World War II, Camp Grant served as one of the largest Army induction and training centers in the United States, training medical personnel, and serving as a prisoner of war confinement center. Following the end of the war, the facility served as a separation center. In 1946, Camp Grant was shut down for the second (and final) time. After World War II, Illinois adopted the Airport Authority Act; the Greater Rockford Airport Authority was created in 1946. In 1948, the Camp Grant land was officially transferred to the airport authority from the federal government. Of the 5,460 acres (plus a 6,000 acre rifle range) of Camp Grant, the airport authority acquired the western 1,500 acres of the facility, bordered by the Rock River to the north and the Kishwaukee River to the south. In 1954, construction commenced on the airport and terminal. The airport demolished the final remaining Camp Grant buildings on the airport property