Sierra Azul Preserve

This preserve has the beauty and ruggedness of an unspoiled wilderness, but has been inhabited by people for a millennia. Native Americans have celebrated their traditions and histories at Mount Umunhum, which figures prominently in the Amah Mutsun people's creation story. German and Austrian refugees of the Franco-Prussian War settled in the area in 1870 to be near the New Almaden Quicksilver mining operations, developing the land for orchards and vineyards. From 1957 to 1980, the Mount Umunhum summit was the site of the Almaden Air Force Station, which served as part of a network of radar stations. The square concrete structure that is still visible was once the base for a large Cold War-era radar sail.

In addition to its unique habitats and geological features, Mount Umunhum has an important role in the region’s local and cultural history. For millennia, Native Americans have celebrated their traditions and histories at Mount Umunhum. The word “Umunhum” means “resting place of the hummingbird”, and signifies the delivery of fire to the Amah Mutsun people.

From 1957 to 1980, the summit was the site of the former Almaden Air Force Station where it served as part of a network of radar stations. The square concrete structure at the top of Mount Umunhum was once the base for a large Cold War-era radar sail. The summit has been closed since 1980 when the base was decommissioned. The base was acquired by the District and added to the Sierra Azul Open Space Preserve in 1986. In 2009, Midpen received federal funding, which enabled Midpen to clean up the site. Over 3,000 cubic yards of hazardous materials, including lead paint, asbestos, fuel storage containers and PCB transformers were removed along with13,680 tons of concrete, asphalt, wood and other materials, 97% of which were recycled or reused.