On a simple east/west basis, Western Oklahoma is popularly considered that part of the state west of I-35.^[1][2] I-35 creates a north/south line through the approximate center of the main body of the state (i.e., without regard for the Oklahoma Panhandle), passing through Oklahoma City, the state capital.^[3]

However, other definitions are possible. For tourism purposes, the Oklahoma Tourism and Recreation Department breaks the state into six regions.^[4] The 14 counties of Southwest Oklahoma, called Great Plains Country, do all fit west of I-35, including the easternmost counties in the grouping, Stephens and Jefferson.^[4][5][6] But, while most of the 16 counties of Northwest Oklahoma, called Red Carpet Country, are also west of I-35, the two easternmost in that grouping, Kay and Noble, each have some land area east of I-35.^[4][7][8] Then, the department includes 12 counties in Central Oklahoma, called Frontier Country, around Oklahoma City.^[4] Portions of that grouping, like Canadian County, are entirely west of I-35.^[9] And, the department has established a South Central grouping of 7 counties, called Chickasaw Country, some of which, like Carter County, have more land west of I-35 than east.^[4][10]