The Ancestral Puebloans (Anasazi) were an ancient Native American culture that spanned the present-day Four Corners region of the United States, comprising southeastern Utah, northeastern Arizona, northwestern New Mexico, and southwestern Colorado. The Ancestral Puebloans are believed to have developed, at least in part, from the Oshara Tradition, who developed from the Picosa culture.

During the period from 700–1130 AD (Pueblo I and II Eras), a rapid increase in population was due to consistent and regular rainfall patterns supporting agriculture. Studies of skeletal remains show that this growth was due to increased fertility rather than decreased mortality.