Southern Illinois Southern Illinois Southern Illinois (also known as "Little Egypt") is the southern third of the state of Illinois. The southern part of Illinois has a unique cultural and regional history. Part of downstate Illinois, the Southern Illinois region is bordered by the two most voluminous rivers in the United States: the Mississippi River and its connecting Missouri River to the west, and the Ohio River to the east and south with the Wabash as tributary. Southern Illinois' most populated city is Belleville at 44,478. Other principal cities include Alton, Centralia, Collinsville, Edwardsville, Effingham, O'Fallon, Harrisburg, Herrin, Mt. Vernon, Marion, and
Vermilion River (Illinois River) in Illinois. Access to a stretch of river around a dam owned by Buzzi Unicem was temporarily barred in 2009 after two drowning deaths that occurred on June 23 and 26, respectively, as well as numerous other boating accidents. The river access was reopened in 2010. The following cities and towns are drained by the Vermilion: The following counties are drained at least in part by the Vermilion River: Vermilion River (Illinois River) The Vermilion River is a tributary of the Illinois River in the state of Illinois, United States. The river flows north, in contrast to a second Vermilion