The land takes its name from Rancho San Antonio, one of the Mexican-era land grants that divided the Santa Clara Valley among a small number of families in the 1830s and 1840s. Juan Prado Mesa received this 7,982-acre grant in 1839, bounded by Adobe Creek to the north and Stevens Creek to the south. The ranching economy that followed -- cattle, then orchards, then dairy -- shaped the landscape that visitors walk through today. Deer Trail, the park's most popular route, follows gentle grades through grasslands and oak groves that once served as pasture. The working ranch era ended when the county and the open space district acquired the land for public use.

The park offers something for every ambition level. Easy loops through the valley floor attract families with strollers and casual walkers. The Wildcat Loop and PG&E Trail climb into steeper terrain with Bay views. More ambitious hikers can connect to Monte Bello Open Space Preserve and climb all the way to the 2,800-foot summit of Black Mountain, a strenuous but rewarding all-day excursion that begins in suburban Los Altos and ends in mountain wilderness. The deer are remarkably tame, accustomed to the foot traffic. Coyotes, bobcats, and the occasional mountain lion inhabit the deeper canyons.

Rancho San Antonio defines the boundary between Silicon Valley's built environment and its wild hinterland. From the ridgelines above the park, the view north encompasses the full sweep of the Bay -- Moffett Field's hangars, the salt ponds, the distant skyline of San Francisco. Turn south and west, and the Santa Cruz Mountains roll away in forested ridges. The park's popularity creates its own challenges: crowded trails, full parking lots, and the constant question of how to manage a wilderness experience for hundreds of thousands of annual visitors. But the crowds themselves are a testament to the park's value. In a region where every acre has a development price, Rancho San Antonio is priceless for what it does not contain.