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.[3] From 1938 to 1955, US 66 City was signed on this particular route as well.[4][5] By 1939, US 67 Alternate was signed after US 67 was rerouted away from East St. Louis.[6] Up until 1964, parts of IL 3, IL 162, and US 67 Alternate utilized present-day IL 203.[7] 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.[2][8]
^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.