Oklahoma may have a reputation as flat prairie land, but the reality is far more sundry. If you’ve ever noticed a variance in the terrain as you travel across the state, your eyes do not deceive you. According to the Oklahoma Tourism and Recreation Department and the Environmental Protection Agency, Oklahoma has the most diverse terrain per square mile of any state in the country.

There are many factors at play in this diversity. The amount of precipitation each year declines steeply across the state from about 55 inches per year in the southeast to around 11 inches per year in the west.

“This gradient of precipitation plays an important role in [Oklahoma’s] diversity,” says Bruce Hoagland, Ph.D., associate chair and professor of the department of geography and environmental sustainability at the University of Oklahoma.

Hoagland goes on to explain that as prevailing wind comes from the west over the Rocky Mountains, it loses moisture in the mountains and enters western Oklahoma as dry air. Concurrently, humid air comes up from the Gulf of Mexico, which causes more precipitation in the east.

The elevation of the state also increases from southeast to northwest, with the Panhandle boasting the highest elevation.

“That increase in elevation is because the Rocky Mountains formed, and it effectively pushed up part of the continent – lifting part of the continent with it,” says Hoagland.

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And the position Oklahoma holds on the continent accounts for much of the variety in ecoregions. 

“Oklahoma is an area of convergence,” says Kurt Lively, Ph.D., associate professor of history at Tulsa Community College who specializes in Oklahoma history. “Oklahoma has a lot of ecological diversity. So each region developed a little differently because of the natural features and rainfall in each area.”

Hoagland seconds: “We’re at a biogeographical crossroads, if you will.”

And that convergence means much of our terrain is spillover from states around us. In eastern Oklahoma, for example, is the edge of the eastern deciduous forest. 

“You find a lot of trees and other vegetation that are more typical of Arkansas, Missouri, Tennessee, Kentucky,” says Hoagland. “You have fairly tall trees and many species of plants that are more characteristic of forests east of us.”

Similarly, in the Panhandle and Black Mesa, there are plants and animals more common to the west and the Rocky Mountains, says Hoagland. 

And in the southwest corner of the state, “there are plants and animals that have more in common with characteristics from the Chihuahuan Desert,” he says. 

Lively continues: “The Western High Plains, for example, has a unique history, due in part to its limited rainfall. Today, it is most suited to cattle ranching.” He also mentions that southwestern Oklahoma is conducive to cotton, north central Oklahoma has a lot of wheat farms, and timber and coal have been more important industries in eastern Oklahoma.

With the diversity of surroundings you can find in Oklahoma, it’s agreed that this land we belong to truly is grand. 

The 12 Terrains 

There are many ways to classify the ecoregions in Oklahoma,
but the Oklahoma Department of Tourism and Recreation has separated them into 12: 
Western High Plains (Panhandle)
Flat and dry at a high elevation
Southwestern Tablelands
Black Mesa, Oklahoma’s highest elevation
Central Great Plains
Most of the western half of the state, from north to south
Tallgrass Prairie
(NORTH CENTRAL)
Iconic tall grass prairies
Crosstimbers
Central Oklahoma from the northern to southern border
East Central Texas Plains
Central southern border, heavily wooded with post oak trees
Caves and Prairie (Northeast)
Grasslands and forest
Ozark Highlands (East)
Heavily forested
Ozark Forest (East)
Illinois River and oak forest
Hardwood Forest
(EAST CENTRAL)
Forested valleys and ridges
Ouachita Mountains (Southeast)
Towering pines in the Ouachita National Forest
Cypress Swamps and Forest
Southeastern border, also known as South Central Plains