The Southwestern United States (called the American Southwest or simply the Southwest) is a region of the western United States. The region is warmer than the northern states and drier than the eastern states. The area includes Arizona and New Mexico, as well as the nearby parts of Southern California, Nevada, Utah, and Colorado and western Texas. The Southwest is growing really fast, big cities in the area are Phoenix, Las Vegas, El Paso, Albuquerque, and Tucson. It is one of the fastest growing parts of the country.