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
Saline River (Illinois) on sandstone bluffs overlooking the Saline River Middle Fork Valley. The following cities and towns are drained by the Saline River: South Fork Middle Fork North Fork The watershed includes all or part of the following counties: Saline River (Illinois) The Saline River is a tributary of the Ohio River, approximately long, in the Southern Illinois region of the U.S. state of Illinois. The river drains a large section of southeast Illinois, with a drainage basin of . The major tributaries include the South Fork, Middle Fork and North Fork, all lying within the Saline Valley. The once meandering swampy