Oklahoma has 41 state parks , six national parks or protected regions , and a network of wildlife preserves and conservation areas . Six percent of the state 's 10 million acres ( 40,000 km2 ) of forest is public land , including the western portions of the Ouachita National Forest , the largest and oldest national forest in the southern United States . With , the Tallgrass Prairie Preserve in north-central Oklahoma is the largest protected area of tallgrass prairie in the world and is part of an ecosystem that encompasses only 10 percent of its former land area , once covering 14 states . In addition , the Black Kettle National Grassland covers of prairie in southwestern Oklahoma . The Wichita Mountains Wildlife Refuge is the oldest and largest of nine national wildlife refuges in the state and was founded in 1901 , encompassing . Of Oklahoma 's federally protected park or recreational sites , the Chickasaw National Recreation Area is the largest , with . Other federal protected sites include the Santa Fe and Trail of Tears national historic trails , the Fort Smith and Washita Battlefield national historic sites , and the Oklahoma City National Memorial
Trail of Tears
Trail of Tears
Geography of Oklahoma