The U.S. Interior Highlands is a mountainous region spanning eastern Oklahoma

Oklahoma

Oklahoma is a state located in the South Central region of the United States of America. With an estimated 3,751,351 residents as of the 2010 census and a land area of 68,667 square miles , Oklahoma is the 28th most populous and 20th-largest state...

, western and northern Arkansas

Arkansas

Arkansas is a state located in the southern region of the United States. Its name is an Algonquian name of the Quapaw Indians. Arkansas shares borders with six states , and its eastern border is largely defined by the Mississippi River...

, southern Missouri

Missouri

Missouri is a US state located in the Midwestern United States, bordered by Iowa, Illinois, Kentucky, Tennessee, Arkansas, Oklahoma, Kansas and Nebraska. With a 2010 population of 5,988,927, Missouri is the 18th most populous state in the nation and the fifth most populous in the Midwest. It...

, and the extreme southeast corner of Kansas

Kansas

Kansas is a US state located in the Midwestern United States. It is named after the Kansas River which flows through it, which in turn was named after the Kansa Native American tribe, which inhabited the area. The tribe's name is often said to mean "people of the wind" or "people of the south...

. The name is designated by the United States Geological Survey to refer to the combined mountainous region of the Ozarks and Ouachita Mountains

Ouachita Mountains

The Ouachita Mountains are a mountain range in west central Arkansas and southeastern Oklahoma. The range's subterranean roots may extend as far as central Texas, or beyond it to the current location of the Marathon Uplift. Along with the Ozark Mountains, the Ouachita Mountains form the U.S...

, which form a distinct physiographic division

Physiographic regions of the world

The physiographic regions of the world are a means of defining the Earth's landforms into distinct regions based upon classic 1916 three-tiered approach defining divisions, provinces, and sections...

. It is the only major highland region between the Rocky Mountains

Rocky Mountains

The Rocky Mountains are a major mountain range in western North America. The Rocky Mountains stretch more than from the northernmost part of British Columbia, in western Canada, to New Mexico, in the southwestern United States...

 and the Appalachian Mountains

Appalachian Mountains

The Appalachian Mountains #Whether the stressed vowel is or ,#Whether the "ch" is pronounced as a fricative or an affricate , and#Whether the final vowel is the monophthong or the diphthong .), often called the Appalachians, are a system of mountains in eastern North America. The Appalachians...

 in the United States

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

.

The region is occupied by the Ozark mountain forests

Ozark Mountain Forests

The Ozark Mountain forests are a temperate broadleaf and mixed forests ecoregion of the central United States delineated by the World Wide Fund for Nature...

, an ecoregion of temperate broadleaf and mixed forests

Temperate broadleaf and mixed forests

Mixed forests are a temperate and humid biome. The typical structure of these forests includes four layers. The uppermost layer is the canopy composed of tall mature trees ranging from 33 to 66 m high. Below the canopy is the three-layered, shade-tolerant understory that is roughly 9 to...

. Parts of the area are covered by three national forests

United States National Forest

National Forest is a classification of federal lands in the United States.National Forests are largely forest and woodland areas owned by the federal government and managed by the United States Forest Service, part of the United States Department of Agriculture. Land management of these areas...

: The Ouachita National Forest

Ouachita National Forest

The Ouachita National Forest is a National Forest that lies in the western portion of Arkansas and portions of eastern Oklahoma.-History:The Ouachita National Forest is the oldest National Forest in the southern United States. The Forest encompasses , including most of the scenic Ouachita Mountains...

 in Oklahoma and Arkansas, the Ozark-St. Francis National Forest

Ozark-St. Francis National Forest

The Ozark – St. Francis National Forest is a United States National Forest that is located in the state of Arkansas. It is composed of two separate forests, Ozark National Forest and St. Francis National Forest, each with their own biological, topographical, and geological differences...

 in Arkansas, and the Mark Twain National Forest

Mark Twain National Forest

Mark Twain National Forest 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 approximately 1.5 million acres , 78,000 acres of which are Wilderness, and National...

in Missouri.