The Southwest differs from the adjoining Midwest in weather (drier), population (less dense), and ethnicity (strong Spanish-American and Native-American components). Outside the cities, the region is a land of open spaces, much of which is desert. The magnificent Grand Canyon is located in this region, as is Monument Valley, the starkly beautiful backdrop for many western movies. Monument Valley is within the Navajo Reservation, home of the most populous American Indian tribe. To the south and east lie dozens of other Indian reservations, including those of the Hopi, Zuni, and Apache tribes.

Parts of the Southwest once belonged to Mexico. The United States obtained this land following the Mexican-American War of 1846-48. Its Mexican heritage continues to exert a strong influence on the region, which is a convenient place to settle for immigrants (legal or illegal) from farther south. The regional population is growing rapidly, with Arizona in particular rivaling the southern states as a destination for retired Americans in search of a warm climate.

Population growth in the hot, arid Southwest has depended on two human artifacts: the dam and the air conditioner. Dams on the Colorado and other rivers and aqueducts such as those of the Central Arizona Project have brought water to once-small towns such as Las Vegas, Nevada; Phoenix, Arizona; and Albuquerque, New Mexico, allowing them to become metropolises. Las Vegas is renowned as one of the world's centers for gambling, while Santa Fe, New Mexico, is famous as a center for the arts, especially painting, sculpture, and opera. Another system of dams and irrigation projects waters the Central Valley of California, which is noted for producing large harvests of fruits and vegetables.