For thousands of years, ancestors of the Acjachemen came to this site to gather chert, a silica-rich hard rock that breaks along fracture lines to produce sharp edges and was therefore valuable for making stone tools such as scrapers, stone points, and knives. Ancient people living in the upper Aliso Creek area visited this site to quarry chert, while others traveled greater distances and lived here for short periods of time. Skyridge was home to one of the largest and oldest quarries in mainland Orange County. This land was excavated in the 1970's and 1980's, and again in the 2010's, and roughly 200,000 pieces of chert were collected, though archaeologists believed millions more were not collected. In the Acjachemen creation story, chert was one of the "kaamalam," meaning "first people," and the Acjachemen believe this quarry represents a living spirit.
