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) 83 and passes the Ape Canyon Trailhead and the Lava Canyon Interpretive Site, both on the left, before entering Muddy River Gorge. Flowing northeast through the gorge, the stream plunges over three waterfalls before emerging from the narrows and curving sharply again to the southeast. Here Crane Lake is on the left, Smith Creek enters from the left, and Smith Creek Trailhead is on the right. Slightly downstream of the trailhead, the river leaves the national volcanic monument but remains in the national forest. At about the level, Clearwater Creek enters from the left. Turning south, the river descends less