The Chicago Mustangs were charter members of the United Soccer Association (USA) in 1967. The league was made up if wholly imported European teams, The Mustangs were actually??Cagliari Calcio??from Italy. In 1968, the USA merged with the National Professional Soccer League (NPSL) to form the North American Soccer League (NASL). The Mustangs left the league and went semi-pro in 1969. They eventually became a feeder team for the Chicago Sting who joined the NASL in 1974.