Some of the first excavations at Hueyatlaco were carried out in 1961, when professor Cynthia Irwin-Williams conducted an extensive dig at the site. Even before she arrived, the region was known as a place rich in animal fossils, which sparked the interest of scholars. Irwin-Williams was soon joined by other prominent persons of the U.S. Geological Survey, notably Virginia Steen-McIntyre, who was responsible for publicizing the find and the magnificent discoveries it entailed. Due to the vast numbers of animal fossils, it was commonly believed that this site was a kill site, where ancient humans butchered the animals they hunted.