Shawnee National Forest

The Shawnee National Forest, located in the Ozark and Shawnee Hills of Southern Illinois, consists of approximately 280,000 acres (1,100 km²) of federally managed lands. In descending order of land area it is located in parts of Pope, Jackson, Union, Hardin, Alexander, Saline, Gallatin, Johnson, and Massac counties. Forest headquarters are located in Harrisburg, Illinois. There are local ranger district offices in Jonesboro and Vienna.
The Shawnee National Forest is also the single largest publicly owned body of land in the state of Illinois.
http://www.fs.usda.gov/shawnee