On a remote mountainside 2,000 meters above sea level in the northern Sierra Madre Oriental, the rockshelter at La Calsada has yielded basic archaeological data for one of the least understood regions of prehistoric North America, the state of Nuevo Leon in northern Mexico. This comprehensive site report, with detailed information on artifacts and stratigraphy, provides baseline data for further explorations in the region and comparisons with other North American hunter-gatherer groups. Radiocarbon dating traces the earliest component at the site to 8600-7500 B.C., giving La Calsada arguably the earliest well-dated lithic complex in Mexico. Nance describes some 1,140 recovered stone tools, with comparisons to the archaeology of southern and southwestern Texas, as well as reported sites in Tamaulipas, Coahuila, and Nuevo Leon, Mexico. From the lithic and stratigraphic analysis, Nance deduces occupational patterns at the site, beginning with Paleo-Indian cultures that lived in the area until about 7500 B.C. Through changes in tool technology, he follows the rise of the Abasolo tradition around 3000 B.C. and the appearance of a new culture with a radically different lithic industry around 1000 A.D.