The Southwestern United States, also known as the American Southwest or simply the Southwest, is a geographic and cultural region of the United States that includes Arizona and New Mexico, along with adjacent portions of California, Colorado, Nevada, Oklahoma, Texas, and Utah. The largest cities by metropolitan area are Phoenix, Las Vegas, El Paso, Albuquerque, and Tucson.[2] Before 1848, in the historical region of Santa Fe de Nuevo México as well as parts of Alta California and Coahuila y Tejas, settlement was almost non-existent outside of Nuevo México's Pueblos and Spanish or Mexican municipalities. Much of the area had been a part of New Spain and Mexico until the United States acquired the area through the Treaty of Guadalupe Hidalgo in 1848 and the smaller Gadsden Purchase in 1854.
While the region's boundaries are not officially defined, there have been attempts to do so.[3] One such definition is from the Mojave Desert in California in the west (117° west longitude) to Carlsbad, New Mexico in the east (104° west longitude); another says that it extends from the Mexico–United States border in the south to the southern areas of Colorado, Utah, and Nevada in the north (39° north latitude).[4] In another definition, the core Southwestern U.S. includes only the states of Arizona and New Mexico; others focus on the land within the old Spanish and Mexican borders of the Nuevo México Province or the later American New Mexico Territory.[5][6][7]
Distinct elements of the Western lifestyle thrive in the region, such as Western wear and Southwestern cuisines, including Native American, New Mexican, and Tex-Mex, or various genres of Western music like Indigenous, New Mexico, and Tejano music styles.[8][9][10][11] Likewise with the sought-after Southwestern architectural styles in the region inspired by blending Pueblo and Territorial styles, with Mediterranean Revival, Spanish Colonial architecture, Mission Revival architecture, Pueblo Deco, and Ranch-style houses in the form of the amalgamated Pueblo Revival and Territorial Revival architectures.[12][13][14][15] This is due to the region's caballero heritage of the Native American (especially Apache, Pueblo, and Navajo), Hispano, Mexican American, and frontier cowboy.[16][17][18][19]
The geography of the region is mainly made up of 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.[20] 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 east, north to south.
Formed approximately 8000 years ago, the Chihuahuan Desert is a relatively dry desert,[21] although it is slightly wetter than the Sonoran Desert to the west.[20] The Chihuahuan Desert spreads across the southeastern portion of the region, covering from southeastern Arizona, across southern New Mexico, and the portion of western Texas included in the Southwest.[21] While it is the second largest desert in the United States,[20] only a third of the desert is within the United States, with the rest in Mexico.[22] El Paso and Albuquerque are the major US cities in this desert, with other smaller cities being Las Cruces and Roswell in New Mexico and Willcox in Arizona.[20]
The elevation in the Chihuahuan varies from about 1,750 to 6,000 feet (500 to 1,800 meters), as there are several larger mountain ranges, such as the Organ Mountains, the Guadalupe Mountains, and the Chiracahua Mountains, plus many smaller mountain ranges contained in the area, namely the Animas, San Andres, and Doña Ana Mountains in New Mexico; and the Franklin, Hueco, and Davis Mountains in Texas. It also reaches up into the foothills of the higher ranges such as the Black Range and Oscura Mountains in New Mexico. High above the desert, these forest-covered and sometimes snow-capped mountains form sky islands, with radically different flora and fauna than the surrounding desert below. The sky islands also supply the surrounding desert foothills with flowing water during the spring runoff and after the summer storms of the New Mexican monsoon season. The Chihuahuan is a "rain shadow" desert, formed between two mountain ranges (the Sierra Madre Occidental on the west and the Sierra Madre Oriental on the east) which block oceanic precipitation from reaching the area.[21] The Chihuahuan Desert is considered the "most biologically diverse desert in the Western Hemisphere and one of the most diverse in the world," and includes more species of cacti than any other desert in the world.[22] The most prolific plants in this region are agave, yucca and creosote bushes,[20] in addition to the ubiquitous presence of various cacti species.
When people think of the desert southwest, the landscape of the Sonoran Desert is what mostly comes to mind.[20] The Sonoran Desert makes up the southwestern portion of the Southwest; most of the desert lies in Mexico, but its United States component lies on the southeastern border of California, and the western 2/3 of southern Arizona. Rainfall averages between 4 and 12 in (100 and 300 mm) per year, and the desert's most widely known inhabitant is the saguaro cactus, which is unique to the desert.[23][24] It is bounded on the northwest by the Mojave Desert, to the north by the Colorado Plateau and to the east by the Arizona Mountains forests and the Chihuahuan Desert.[25] Aside from the trademark saguaro, the desert has the most diverse plant life of any desert in the world,[23] and includes many other species of cacti, including the organ-pipe, senita, prickly pear, barrel, fishhook, hedgehog, cholla, silver dollar, and jojoba.[23][24] The portion of the Sonora Desert which lies in the Southwestern United States is the most populated area within the region. Six of the top ten major population centers of the region are found within its borders: Phoenix, Tucson, Mesa, Chandler, Glendale, and Scottsdale, all in Arizona. Also within its borders are Yuma and Prescott Arizona.[20]
The most northwest portion of the American Southwest is covered by the Mojave Desert. Bordered on the south by the Sonoran Desert and the east by the Colorado Plateau, its range within the region makes up the southeast tip of Nevada, the southwestern corner of Utah and the northwestern corner of Arizona.[24] In terms of topography, the Mojave is very similar to the Great Basin Desert, which lies just to its north.[20] Within the region, Las Vegas is the most populous city; other significant population centers include Laughlin and Pahrump in Nevada, St. George and Hurricane in Utah, and Lake Havasu City, Kingman, and