Francisco Estrada's rancho occupied the flat valley floor between the foothills of the Santa Cruz Mountains and the marshlands of the Bay. The terrain was ideal for grazing: open grasslands, mild climate, and seasonal creeks that provided water for livestock. The name 'Pastoria de las Borregas' tells you exactly what happened here -- ewes grazed on the pasture, wool was sheared, and lambs were raised for meat and market. The rancho economy was simple, self-sufficient, and entirely dependent on the land's natural productivity.

No former rancho in California has changed more dramatically than Rancho Pastoria de las Borregas. The flat terrain that made it good sheep pasture also made it ideal for the suburban development and office park construction that arrived in the mid-twentieth century. Sunnyvale became home to Lockheed, then to a succession of semiconductor and electronics companies. Mountain View became Google's headquarters. The rancho's 9,066 acres now contain some of the most valuable commercial real estate in the world, supporting an economy measured in billions rather than in bales of wool.

Almost nothing visible connects present-day Sunnyvale and Mountain View to Francisco Estrada's sheep pasture. The creeks have been channelized or buried. The grasslands have been paved. The adobe structures of the rancho era are gone. But the flat geography persists -- it is the same level terrain that attracted sheep ranchers in 1842 and tech campuses in 2002. Rancho Pastoria de las Borregas is a reminder that Silicon Valley's most fundamental resource has always been its land, valued differently by each generation but continuously in use.