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
Fox River (Little Wabash tributary) Fox River: Fox River (Little Wabash tributary) The Fox River is a tributary of the Little Wabash River in southern Illinois. It rises in Jasper County to the southeast of Newton and flows south past Olney, then joins the Little Wabash at the northeast corner of Edwards County, near Mt. Erie. The river is in length. There is a smaller "Fox River" that is a tributary of the Wabash River in southern Illinois, entering the Wabash near New Harmony, Indiana. The following cities, towns and villages are in the Fox River watershed: The following counties are at least partially drained