Starting sometime after A.D. 1250 the Anasazi moved out of San Juan County, often walking away from their settlements as though they intended to return in a few minutes - or so it looks. Why did they leave behind their beautiful cooking pots and baskets? Perhaps because they had no means to transport them. When forced to migrate a long distance, it was more efficient to leave the bulky items and replace them after they reached their destination.

We do know that they moved south. Classic late Mesa Verde-style settlements can still be recognized in New Mexico and Arizona, in high, defensible locations in areas where the local Anasazi sites look quite different. By A.D. 1400 almost all the Anasazi from throughout the Southwest had aggregated into large pueblos scattered through the drainages of the Little Colorado and Rio Grande rivers in Arizona and New Mexico. Their descendants are still there in the few surviving pueblos.

Why did they leave? It is impossible to find a single cause that can explain it, but there appear to be several that contributed. First, the climate during the Pueblo III period was somewhat unstable with erratic rainfall patterns and periods of drought. This weather problem climaxed with a thirty-year drought starting about 1270 that coincided with a cooling trend that significantly shortened the growing season. Perhaps the expanding population had pressed the limits of the land's capacity to support the people so that they were unable to survive the climatic upheavals of the thirteenth century.

Could they have been driven out by nomadic tribes, such as Utes or Navajos? There is no direct evidence that either group, or any other like them, was in the area that early. There is mounting evidence, however, that the Numic-speaking peoples, of whom the Utes and Paiutes are part, had spread northwestward out of southwestern Nevada and were in contact with the Pueblo-like peoples of western Utah by A.D. 1200. It is certainly possible that they were in San Juan County shortly after that. Ute and Paiute sites are very difficult to distinguish from Anasazi campsites, and we may not be recognizing them. Navajos were in northwestern New Mexico by 1500, but we do not know where they were before that. Perhaps the answer to the Anasazis' departure from Utah lies in a combination of the bad-climate and the arriving-nomads theories.

See: J. Richard Ambler and Marc Gaede, The Anasazi (1977); and Linda S. Cordell, Prehistory of the Southwest (1984).