Oklahoma Panhandle in the context of Oklahoma Territory

The Texas panhandle is a region of the U.S. state of Texas consisting of the northernmost 26 counties in the state. The panhandle is a square-shaped area bordered by New Mexico to the west and Oklahoma to the north and east. It is adjacent to the Oklahoma Panhandle, land which Texas previously claimed. The 1820 Missouri Compromise declared no slavery would be allowed in states admitted from the Louisiana Purchase above 36°30′ north latitude. Texas was annexed in 1845 from still more westerly land. The Compromise of 1850 removed territory north of this line from Texas, and set the border between the Texas Panhandle and the New Mexico Territory at the 103rd meridian west. The eastern border at the 100th meridian west was inherited from the Adams–Onís Treaty of 1819, which defined the border between the United States and New Spain. The Handbook of Texas defines the southern border of Swisher County as the southern boundary of the Texas Panhandle region.

Its land area is 25,823.89 sq mi (66,883.58 km), or nearly 10% of the state's total. The Texas Panhandle is slightly larger in size than the US state of West Virginia. An additional 62.75 sq mi (162.53 km) is covered by water. Its population as of the 2010 census was 427,927 residents, or 1.7% of the state's total population. As of the 2010 census, the population density for the region was 16.6 per square mile (6.4/km). However, more than 72% of the Panhandle's residents live in the Amarillo Metropolitan Area, which is the largest and fastest-growing urban area in the region. Despite being geographically the northernmost part of Texas, the Panhandle is distinct from the region commonly called "North Texas", which is to the south and east.

The High Plains are a subregion of the Great Plains, mainly in the Western United States, but also partly in the Midwest states of Nebraska, Kansas, and South Dakota, generally encompassing the western part of the Great Plains before the region reaches the Rocky Mountains. The High Plains are located in eastern Montana, southeastern Wyoming, southwestern South Dakota, western Nebraska, eastern Colorado, western Kansas, eastern New Mexico, the Oklahoma Panhandle, and the Texas Panhandle. The southern region of the Western High Plains ecology region contains the geological formation known as Llano Estacado which can be seen from a short distance or on satellite maps. From east to west, the High Plains rise in elevation from around 1,500 to 6,000 ft (460 to 1,830 m).

On a simple east/west basis, Western Oklahoma is popularly considered that part of the state west of I-35. 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.

However, other definitions are possible. For tourism purposes, the Oklahoma Tourism and Recreation Department breaks the state into six regions. 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. 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. Then, the department includes 12 counties in Central Oklahoma, called Frontier Country, around Oklahoma City. Portions of that grouping, like Canadian County, are entirely west of I-35. 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.