Southern Illinois the Ozarks of Missouri, is chiefly in southern Jackson, Union, northern Alexander and Johnson counties. The eastern area, more closely related to the Wabash Valley Seismic Zone, is mostly in northern Pope, southern Saline, Gallatin, eastern Johnson and southern Williamson counties. The Shawnee National Forest covers a large territory, including seven wilderness areas: Garden of the Gods, Bay Creek, Clear Springs, Bald Knob, Burden Falls, Lusk Creek, and Panthers Den. Of southern Illinois' rivers, only the Mississippi and the Ohio are navigable for modern commerce. The Big Muddy River, Marys River, Saline River and Cache River run their courses in
Muddy River (Washington) rapidly, passing under Forest Road 25 and then receiving Clear Creek from the left about from the mouth. At the road crossing, Muddy Creek Picnic Site is on the left. Below the confluence with Clear Creek, the river meanders through Cedar Flats, leaves the national forest slightly more than a mile from the mouth, and passes a United States Geological Survey (USGS) stream gauge, on the left from the mouth. Muddy River enters the Lewis River about from the larger stream's mouth on the Columbia River. The USGS monitors the flow of Muddy River at a station upstream of the