Chocolate is "period" in the American southwest

A paper by Patricia L. Crown, of the Department of Anthropology, University of New Mexico, and W. Jeffrey Hurst, of The Hershey Center for Health and Nutrition, published on the PNAS website, explores the evidence of the use of cacao in the 11th and 12th centuries in the American Southwest.

Abstract from the paper entitled Evidence of cacao use in the Prehispanic American Southwest:

Chemical analyses of organic residues in fragments of ceramic vessels from Pueblo Bonito in Chaco Canyon, New Mexico, reveal theobromine, a biomarker for cacao. With an estimated 800 rooms, Pueblo Bonito is the largest archaeological site in Chaco Canyon and was the center of a large number of interconnected towns and villages spread over northwestern New Mexico. The cacao residues come from pieces of vessels that are likely cylinder jars, special containers occurring almost solely at Pueblo Bonito and deposited in caches at the site. This first known use of cacao drinks north of the Mexican border indicates exchange with cacao cultivators in Mesoamerica in a time frame of about A.D. 1000–1125. The association of cylinder jars and cacao beverages suggests that the Chacoan ritual involving the drinking of cacao was tied to Mesoamerican rituals incorporating cylindrical vases and cacao. The importance of Pueblo Bonito within the Chacoan world likely lies in part with the integration of Mesoamerican ritual, including critical culinary ingredients.

The entire paper may be found on the PNAS website.