Los Trancos Open Space Preserve
A fence line runs through Los Trancos Open Space Preserve that does not quite line up. The posts on one side are offset from those on the other by several feet -- not from sloppy construction but from the ground itself moving. The San Andreas Fault runs for about a mile beneath this 274-acre preserve near Los Altos Hills, and the evidence of that presence is everywhere: offset fences, sag ponds, pressure ridges, and a 1.5-mile interpretive trail that follows the main rupture caused by the 1906 San Francisco earthquake. Guided "quake walks" are held roughly once a month, making this one of the few places on Earth where you can take a docent-led tour of a major fault line.
The Fault Beneath Your Feet
The San Andreas Fault is California's most famous geological feature, a 750-mile transform boundary where the Pacific Plate grinds northward past the North American Plate at about an inch and a half per year. At Los Trancos, the fault's traces are visible to anyone who knows where to look. Interpretive stations along the earthquake trail point out features created by the 1906 quake and subsequent movement: benches in the hillside where blocks of earth have dropped, ridges pushed up by compression, and the misaligned fence that serves as a visceral demonstration of tectonic displacement. The preserve sits in the Santa Cruz Mountain foothills, protecting the headwaters of Los Trancos Creek, a tributary of San Francisquito Creek.
Saved by the Cost of Sewers
The land that became Los Trancos Open Space Preserve was once part of a 13,300-acre rancho. State senator Louis Oneal purchased it in the early 1900s to raise horses. It was sold to a developer in the 1950s, and power and water lines were installed in the 1960s. Then the city of Palo Alto calculated the cost of providing city services -- sewers, roads, fire protection -- to the remote hillside location, and the development was abandoned. The Midpeninsula Regional Open Space District acquired the preserve in 1976, turning a failed real estate venture into permanent public land. It is a small preserve by regional standards, with about five miles of hiking trails, 2.1 miles open to equestrians and none to bicycles.
Walking the Edge
Hiking Los Trancos feels different from other Peninsula preserves because of what lies underfoot. The trails wind through oak woodland and grassland, offering views of the surrounding hills, but the interpretive signs keep redirecting attention downward. Here the ground dropped. There the hillside buckled. That pond formed in a depression created by fault movement. The preserve reminds visitors that the Bay Area's landscape is not fixed scenery but an active construction zone, continuously reshaped by forces operating on timescales that make the tech industry's rapid cycles look glacial. The next significant earthquake on this section of the San Andreas could happen in decades or centuries, but the evidence of the last one is still legible in the soil.
From the Air
Los Trancos Open Space Preserve is at 37.33°N, 122.18°W in the foothills near Los Altos Hills, along Page Mill Road. The preserve is a small forested area on the ridgeline above Interstate 280. The San Andreas Fault runs through it. Nearby airports: Palo Alto (KPAO), San Carlos (KSQL). Best viewed at 3,000-5,000 ft AGL.