IL 203 is a major north–south artery through the eastern part of the Greater St. Louis metropolitan area.
History
By 1937, US 67 was signed on part of present-day IL 203. From 1938 to 1955, US 66 City was signed on this particular route as well. By 1939, US 67 Alternate was signed after US 67 was rerouted away from East St. Louis. Up until 1964, parts of IL 3, IL 162, and US 67 Alternate utilized present-day IL 203. In 1964, IL 203 was signed; replacing these routes. It originally traveled to Hartford, but this was later trimmed back to I-270 as of 1989.
^Illinois Division of Highways (1955). Illinois Official Highway Map (Map). [1:805,000]. Springfield: Illinois Division of Highways – via Illinois Digital Archives.
^Illinois Division of Highways; H.M. Gousha (1963). Illinois Official Highway Map (Map). [1:790,00]. Springfield: Illinois Division of Highways – via Illinois Digital Archives.
^Illinois Department of Transportation (1989). Illinois Highway Map (Map) (1989–1990 ed.). [1:762,500]. Springfield: Illinois Department of Transportation – via Illinois Digital Archives.