Rancho San Antonio County Park is a public recreational area in the Santa Cruz Mountains, Santa Clara County, in northern California. Saint Joseph's College was once on this land. The adjacent Rancho San Antonio Open Space Preserve is part of the Midpeninsula Regional Open Space District, which manages both the Open Space Preserve and the County Park. Both areas protect much of the upper watershed of Permanente Creek, except the portion in Lehigh Quarry. Together, they are approximately 4,078 acres (16.50 km2) in area and contain 23 miles (37 km) of hiking trails.