Illinois River 20 miles (32 km) of its course, the Illinois is separated from the Mississippi River by only about five miles, by a peninsula of land that makes up Calhoun County. The Illinois joins the Mississippi near Grafton, approximately 25 miles (40 km) northwest of downtown St. Louis and about 20 miles upstream from the confluence of the Missouri River and the Mississippi. South of Hennepin, the Illinois River is following the ancient channel of the Mississippi River. The Illinoian Stage, about 300,000 to 132,000 years ago, blocked the Mississippi near Rock Island, diverting it into its present channel. After the
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