Rancho San Antonio County Park, County park in Santa Clara County, US

Rancho San Antonio County Park covers 289 acres beside the 3,988-acre Open Space Preserve in the Santa Cruz Mountains, bordered by Los Altos and Cupertino. Open grass rises toward wooded hills, with isolated trees and bushes on the slope. Ridges hold grassland and scattered oaks; cooler north-facing slopes carry oaks and bays, hotter south-facing slopes chaparral of chamise, manzanita and birch-leaf mountain mahogany. Permanente Creek flows year round through the county park.

The Ohlone lived here for over 3,000 years at a large village called Partacsi. In March 1776 Juan Bautista de Anza camped at the arroyo of San Joseph Cupertino (now Stevens Creek) and spotted San Francisco Bay from the hill later called De Anza's Knoll. Governor Alvarado granted Rancho San Antonio to Juan Prado Mesa in 1839; William A. Dana bought it in 1853. The Catholic Church bought the land in 1923 and built Saint Joseph's College and the Maryknoll Seminary in 1926. The county bought 130 acres in 1977 and 35 more in 1981.

Deer Hollow Farm, a ten-acre working homestead within the park, keeps Santa Clara County's agricultural history visible: it still produces food on site and is funded jointly by the City of Mountain View, the Midpeninsula Regional Open Space District, Santa Clara County and the Friends of Deer Hollow Farm. Visitors can watch and take part in farm work.

Access from Los Altos is via Foothill Expressway, then Moody Road to Craig Drive; the preserve is entered through the county park, reachable from the Townsgate Drive entrance. Permanente Creek flows year-round along about two miles inside the county park. Signs at the preserve entrance and trail map stations warn of mountain lions, which are tracked.

Deer Hollow Farm within the park is a working farm with organic gardens and farm animals that shows visitors traditional farming methods. This hands-on place helps both children and adults understand where food comes from and how it is grown.