Oklahoma has four mountain ranges. The Ozarks (sometimes referred to as a plateau) in northeast Oklahoma rise from the plains to a height of more than 2,000 feet. The Ouachita Mountains (including the neighboring Kiamichi Mountains) are pine-covered peaks located in southeast Oklahoma. While most mountain ranges run north-south, the ridge lines of the Ouachita’s run east-west. The Ouachitas, which have a rougher topography than any other region in the state, are the highest mountain range between the Rocky Mountains and the Appalachian Mountains. In southwest Oklahoma, the Wichita Mountains, now ranging from 600 to 2,475 feet and covered with granite boulders, were once as high as the Rocky Mountains. The ancient Arbuckle Mountains of south central Oklahoma are composed of limestone, shale, granite and sandstone.
Grasslands are abundant in Oklahoma. Tallgrasses are found in the northern and eastern sections of the state, most notably at the Tallgrass Prairie Preserve, a 39,000-acre property of the Nature Conservancy with free-ranging buffalo, while grasses in the western section are primarily short and mixed. The Black Kettle National Grasslands near Cheyenne in western Oklahoma lies within the limits of the Anadarko Basin, a prolific oil and gas-producing region, giving rise to oil and gas wells on the grasslands, where free-roaming cattle also graze.
Because 24 percent of Oklahoma’s topography—nearly 10 million acres—is forest, the state ranks ninth in the nation for timber production. The largest sawmill east of the Rocky Mountains is located in Oklahoma. In the Ouachita Mountains and the Ozark Plateau in the eastern part of the state, hardwoods predominate. In the mountainous southeast, the forests are dense with pine and oak trees. Through central Oklahoma, post oak and blackjack oak dot the tallgrass prairies, pastures, and croplands. In the southwest, oak shinnery and mesquite spread onto rangeland. Oklahoma has 144 native species of trees including pecan, walnut, pine, several types of oak, and cottonwood. In the fall, the sugar maple and Caddo maple of Caddo County are no less colorful than the maples of New England. Fall color is most prominent in the Ouachita National Forest of southeast Oklahoma.
Oklahoma’s terrain is dominated by two major river basins. Northern and central Oklahoma are in the drainage basin of the Arkansas River; the remainder of the state is in the drainage basin of the Red River. Oklahoma has more man-made lakes than any other state, with more than one million surface acres of water and more miles of shoreline than the Atlantic and Gulf coasts combined. The Grand Lake O’ The Cherokees in northeast Oklahoma has more miles of shoreline than the coast of California.