Los Trancos Open Space Preserve is a 274-acre protected area near Los Altos Hills spanning San Mateo and Santa Clara counties. Once part of a 13,300-acre rancho, this section was bought in the early 1900s by state senator Louis Oneal for raising horses, later passed to a developer, and was acquired by the Midpeninsula Regional Open Space District in 1976 after building plans were abandoned. Today the preserve has about 5 miles of trails and protects the headwaters of Los Trancos Creek. Its most notable feature is roughly a mile of the San Andreas Fault, including a trail that follows the break from the 1906 San Francisco earthquake.