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
Muddy River (Nevada) the Meadow Valley Wash, forming the principal drainage system for southeastern Nevada. The Moapa Valley area is home to a wide variety of rare and endangered species, including fish, invertebrates, birds, and plants. Three endangered fish inhabit the area: the Moapa dace ("Moapa coriacea"), the Virgin River chub ("Gila seminuda"), and the White River springfish ("Crenichthys baileyi moapae"). These species can be found throughout the various springs, called the Muddy Springs, that feed the Muddy River. The U.S. Fish and Wildlife Service has created the Moapa National Wildlife Refuge at the Warm Springs Natural Area, as part of the Desert