The geography of Texas spans a wide range of features and timelines. Texas is the southernmost part of the Great Plains, which ends in the south against the folded Sierra Madre Oriental of Mexico. It is in the south-central part of the United States of America. It is considered to form part of the U.S. South and also part of the U.S. Southwest. The Rio Grande, Red River and Sabine River all provide natural state lines where Texas borders Oklahoma on the north, Louisiana and Arkansas on the east, New Mexico on the west, and the Mexican states of Chihuahua, Coahuila, Nuevo León, and Tamaulipas to the south. By residents, the state is generally divided into North Texas, East Texas, Central Texas, South Texas, and West Texas, but according to the Texas Almanac, Texas has four major physical regions: Gulf Coastal Plains, Interior Lowlands, Great Plains, and The Basin and Range Province. This is the difference between human geography and physical geography. Some regions of Texas are associated with the South more than with the Southwest (primarily East Texas, Central Texas, and North Texas), while other regions share more similarities with the Southwest (primarily far West Texas and South Texas). The upper Texas Panhandle and the South Plains parts of West Texas do not easily fit into either category. The former has much in common with the Midwestern United States, while the latter, originally settled primarily by anglo Southerners, yet with a notable Hispanic population, is somewhat of a blend of South and Southwest. ------------------------------------- The size of Texas prohibits easy categorization of the entire state wholly in any recognized region of the United States; geographic, economic, and even cultural diversity between regions of the state preclude treating Texas as a region in its own right.