United States, Southwest

The southwest is an arid region of high surface relief and relatively low population density. The four states within the region are Arizona, Nevada, New Mexico, and Utah. As of 2005, Arizona is 114,006 square miles and ranks as the 6th largest state; it has an estimated population of 5,939,292 and is the 18th most populated state. Nevada is 110,567 square miles and ranks as the 7th largest state; it has an estimated population of 2,414,807 and is the 35th most populated state. New Mexico is 121,593 square miles and ranks as the 5th largest state; it has an estimated population of 1,928,384 and is the 36th most populated state. Finally, Utah is 84,904 square miles and ranks as the 13th largest state; it has an estimated population of 2,469,585 and is the 34th most populated state. As the numbers indicate, all four states are relatively large in area and rank low in population. Each of these states has its own unique physical and cultural characteristics and all of them share certain attributes as well. The four-state region is part of the larger area characterized as the Empty Quarter by journalist Joel Garreau in his 1981 book The Nine Nations of North America because of its low population densities.

The region is representative of the widespread dry climates of the western United States. Specifically, each of the states has extensive areas of desert, steppe, and undifferentiated highlands. Seasonal temperature regimes range from cool to cold winters and mild to cool summers and much of the variation is attributable to changes in altitude. Precipitation is decidedly on the low side with some areas receiving less than 10 inches per year and others averaging between 10 and 20 inches per year. Vegetation found in this four-state region includes broadleaf deciduous and a variety of coniferous species including ponderosa pine, piñon, and juniper. The latter two tend to grow within the same location resulting in extensive areas of piñon and juniper forests. Unique within the region is the saguaro cactus found in Arizona and northern Mexico. The saguaro cactus grows upward of 12 feet or more and has curving branches, white flowers, and an edible red fruit. The soils in the region are primarily aridisols reflective of the dry climate and mountain soils found within its many uplands and mountainous areas. The region is marked by decidedly rugged and angular mountainous terrain. This characteristic is due to the relative geologic youth of mountains in the west, which have yet to become eroded and rounded like the Appalachian complex in the east.

Culturally, the region is quite diverse. Anglo, Latino, and Native American peoples have coexisted for years within this four-state region. The Native American cohort was, of course, the first inhabitant and its tenure in the region dates back over 10,000 years. Latino presence dates from the early years of Spanish exploration in the 17th century. The Anglo contingent arrived during the western expansion in the mid-19th century.

Perhaps the earliest formal international land route in North American history was the Camino Real (the Royal Road), which began in Mexico City and followed a generally northward course connecting the capitals of the Spanish colonial territory. The colonial centers and inclusive dates of occupation in New Mexico included San Juan Pueblo (1598–1600) and San Gabriel (1600–09), both places located within a few miles of each other and approximately 50 miles north of Santa Fe, the Spanish colonial capital of longest duration (1609–1821). When Mexico achieved independence, the Camino Real was no longer considered a royal route but was nonetheless used extensively for years to come. The Camino Real entered the region at Ciudad Juárez and El Paso and then followed the rift valley northward through current day Las Cruces, Fort Selden, Socorro, Isleta Pueblo, Albuquerque, Santa Fe, San Juan Pueblo, and San Gabriel. The route followed closely the valley of the Rio Grande River and other land routes of the period. In the modern era, Interstate 25 follows essentially the same route as far as [Page 1854]Santa Fe before turning to the east and then north to Raton before crossing into Colorado.

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