Chaco Culture National Historical Park is a United States National Historical Park hosting the densest and most exceptional concentration ofpueblos in the American Southwest. The park is located in northwestern New Mexico, between Albuquerque and Farmington, in a remote canyon cut by the Chaco Wash. Containing the most sweeping collection of ancient ruins north of Mexico, the park preserves one of the United States' most important pre-Columbian cultural and historical areas.Between AD 900 and 1150, Chaco Canyon was a major center of culture for the Ancient Pueblo Peoples. Chacoans quarried sandstone blocks and hauled timber from great distances, assembling fifteen major complexes which remained 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.