 Archeologists estimate that between of arable land was available to Chacoan farmers, whose crops could support approximately 4,000 people.Archeomagnetic analysis indicates the Chetro Ketl field was last used in 1250.Studies of ancient corn cobs found at Pueblo Bonito suggest that large quantities of the foodstuff were imported to the canyon from the Chuska Mountains, west, and the San Juan and Animas River areas, north.