St. Louis Downtown Airport (IATA: CPS, ICAO: KCPS, FAA LID: CPS) is a public-use airport located in Greater St. Louis, one mile (2 km) east of the central business district of Cahokia, in St. Clair County, Illinois, United States. It is owned by the Bi-State Development Agency. The airport is located less than 3 miles from the Gateway Arch Riverfront and is used by many business aircraft visiting the St. Louis region.