<P> The Geography of Oklahoma encompasses terrain and ecosystems ranging from arid plains to subtropical forests and mountains . Oklahoma contains 10 distinct ecological regions , more per square mile than in any other state by a wide margin . It is situated in the Great Plains and U.S. Interior Highlands region near the geographical center of the 48 contiguous states . Usually considered part of the South Central United States , Oklahoma is bounded on the east by Arkansas and Missouri , on the north by Kansas , on the northwest by Colorado , on the far west by New Mexico , and on the south and near - west by Texas . </P>
oklahoma 's 10 geographic regions are defined by surface features called
ecological regions