Between CE 900 and 1150, Chaco Canyon is a major center of culture for the Ancient Pueblo Peoples.
Chacoans quarry sandstone blocks and haul timber from great distances, assembling fifteen major complexes that remain the largest buildings in North America until the 19th century.
Evidence of archaeoastronomy at Chaco has been proposed, with the "Sun Dagger" petroglyph at Fajada Butte a popular example.
Many Chacoan buildings may have been aligned to capture the solar and lunar cycles, requiring generations of astronomical observations and centuries of skillfully coordinated construction.
[ Climate change is thought to have led to the emigration of Chacoans and the eventual abandonment of the canyon, beginning with a fifty-year drought commencing in 1130.
