Southwestern USA

The Southwestern United States (also known as the American Southwest) is a region of the United States which includes Arizona, the western portion of New Mexico, bordered on the east by the Llano Estacado, southern Colorado and Utah below the 39th parallel, the "horn" of Texas below New Mexico, the southernmost triangle of Nevada, and the most southeastern portion of California, which encompasses the Mojave and Colorado Deserts.

The population of the area is around 11 million people, with over half that in Arizona; the most populous cities are Phoenix, El Paso, Las Vegas, Albuquerque, and Tucson.

Most of the area was part of the Viceroyalty of New Spain in the Spanish Empire before becoming part of Mexico. It became part of the United States through the Treaty of Guadalupe Hidalgo and the Gadsden Purchase.

The geography of the region is mainly made up by four features: the Mojave, Sonoran, and Chihuahuan Deserts, and the Colorado Plateau; although there are other geographical features as well, such as a portion of the Great Basin Desert. The deserts dominate the southern and western reaches of the area, while the plateau (which is largely made up of high desert) is the main feature north of the Mogollon Rim. The two major rivers of the region are the Colorado River, running in the northern and western areas, and the Rio Grande, running in the south.

...
Wikipedia