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
Big Sandy Creek (Illinois) two streams combine shortly before discharging into the Illinois River opposite the hamlet of Montezuma, Illinois. Sand discharged by the alluvial creeks may have helped form McEvers Island, a silt island in the Illinois River just below the mouth of the creek. Big Sandy Creek (Illinois) Big Sandy Creek, often called the "Big Branch", is a tributary of the Illinois River in central Illinois. It drains a large portion of southwestern Morgan County and southern Scott County. The drainage of Big Sandy Creek includes Lake Jacksonville and the county seat of Scott County, Winchester, Illinois. Most of the Big Sandy