The farther back in time we go, the more imperfect our knowledge. Before the invention of writing, we have the notoriously undependable oral histories. We also have the more reliable archaeological findings—also imperfect, but the best evidence available. In the late 1970s, a flood control project in El Paso's Upper Valley required an archaeological survey before construction. The survey uncovered remnants of an ancient village. The exact time of occupation is uncertain, but appears to be around 4,000 years ago, give or take a few hundreds of years. Early testing suggested some 23 pit houses, and extrapolation indicates there might be as many as 40.
The Keystone site is the oldest known village site in the western part
of the United States and adjacent northern Mexico. Now protected, the village is being
developed as a scientific and educational site. With further investigation, we should
be able to narrow down the time of occupancy and the village size. It all goes to show
that our Chihuahuan Desert was attractive real estate even long before the Christian
Era. 
Contributor: Arthur H. Harris, Laboratory for Environmental Biology, Centennial Museum, University of Texas at El Paso.
Desert Diary is a joint production of the Centennial Museum and KTEP National Public Radio at the University of Texas at El Paso.
O'Laughlin, T. C. 1980. The Keystone Dam Site And Other Archaic and Formative Sites in Northwest El Paso, Texas. Contributions by Anne C. Cully and Karen H. Clary, Rex E. Gerald, Principal Investigator and Editor. Centennial Museum Publications in Anthropology, 8.