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 3,068,800 acres (12,419 km2) of which 1,506,100 acres (6,095 km2) is public owned, 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.