Chaco Canyon is a historical national monument located in the northwest corner of New Mexico. It along with Mesa Verde are the crown jewels of what remains architecturally of the Anasazi culture of the American Southwest. Also known as the Ancestral Puebloans, the Anasazi inhabited the greater four corners region from about 200 A.D. until 1300 A.D. Many theories have been presented regarding their migration away from the region, but one thing is fairly clear, that the climate changed enough to make their settled agricultural lifestyle harder and harder to maintain. Current descendents of the Anasazi, include the Hopi of Arizona and the Zuni of New Mexico.
Suggested Reading:
Archeoastronomy of the Chacoan Pueblo (PDF)
House of Rain: Tracking a Vanished Civilization Across the American Southwest – Craig Childs
The Lost World of the Old Ones: Discoveries in the Ancient Southwest – David Roberts
Non-Technical Canyon Hiking Guide to the Colorado Plateau – Mike Kelsey
Grand Gulch, Cedar Mesa Plateau Maps – National Geographic Trails Illustrated Maps