Rancho San Antonio County Park and Rancho San Antonio Open Space Preserve are a conjoined public recreational area in the Santa Cruz Mountains, in the northwest quadrant of Santa Clara County, California. The County Park is bordered by Los Altos with some parts of the eastern part of the County Park in western Cupertino. The Open Space Preserve is on the west side of the County Park, also bordered by Los Altos Hills, Monte Bello Open Space Preserve, and the Permanente Quarry.The Midpeninsula Regional Open Space District manages both the 3188 acre Open Space Preserve and the 289 acre County Park.This article covers both Rancho San Antonio County Park and Rancho San Antonio Open Space Preserve.HistoryThe Ohlone Indians lived in the area for over 3,000 years prior to the arrival of the Spanish. A large village, known as Partacsi, was located in the general area.In March 1776, Juan Bautista de Anza led the first overland expedition to San Francisco Bay from Monterey through this area. In de Anza's diary on March 25, 1776, he states that he "arrived at the arroyo of San Joseph Cupertino (now Stevens Creek), which is useful only for travelers. Here we halted for the night, having come eight leagues in seven and a half hours. From this place we have seen at our right the estuary which runs from the port of San Francisco." A prominent hill between Permanente and Stevens Creeks is referred to as "De Anza's Knoll" and marks the location where the explorer first spotted the Bay.