A recent study — the largest of its kind ever conducted — analyzed nearly 200 samples of pottery from Southwestern archaeological sites, ranging from Colorado to Chihuahua and spanning 650 years of human occupation. The results revealed that more than 20 percent of the ceramics contained traces of either cocoa or a potent concoction known as ‘black drink,’ made from yaupon holly, known to scientists as Ilex vomitoria.
what is most interesting is not that caffiene beverages were used, but that the plants didn't grow there...so this implied an active trade network.
“There are no known plants in the Southwest or Northwestern Mexico that have caffeine,” said Dr. Patricia Crown, an anthropologist at the University of New Mexico who led the study.
“So these caffeinated drinks required acquiring — through exchange or direct acquisition — materials from a distance: Mesoamerica, for either plant, or perhaps the Gulf Coast for the holly.”
the "black drink" made from a holly type plant is discussed HERE.
wikipedia article HERE.
more on Yaupon holly HERE.
and during the American Civil war, Yaupon tea was used as a substitute for imported tea or coffee...