Mark Twain National Forest (MTNF) is a U.S. National Forest located in the southern half of Missouri. MTNF was established on September 11, 1939. It is named for author Mark Twain, a Missouri native. The MTNF covers 1,491,840 acres (600,000 ha), 78,000 acres (320 km²) of which are Wilderness, and National Scenic River area. MTNF spans 29 counties and represents 11% of all forested land in Missouri. MTNF is divided into six distinct ranger districts: Ava-Cassville-Willow Springs, Eleven Point, Houston-Rolla-Cedar Creek, Poplar Bluff, Potosi-Fredericktown, and the Salem. The six ranger districts actually comprise nine overall unique tracts of forests. Its headquarters are in Rolla, Missouri.
Some unique features of the Mark Twain include Greer Spring, which is the largest spring on National Forest land, pumping an average of 214 million gallons of water per day. The public can also visit the Glade Top Trail National Scenic Byway, which offers views of over 30 miles (48 km) to the Boston Mountains in Arkansas.