Mount Umunhum from the northeast
|Elevation||3,489 ft (1,063 m) NAVD 88|
|Prominence||586 ft (179 m)|
|Location||Santa Clara County, California, United States|
|Range||Santa Cruz Mountains|
|Topo map||USGS Los Gatos|
|Age of rock||Oligocene|
|Easiest route||None (closed to public, restricted access)|
Mount Umunhum (Ohlone, meaning resting place of the hummingbird) is the fourth-highest peak in the Santa Cruz Mountains of California (after Loma Prieta, Crystal Peak, and Mt. Chual). The mountain is situated in Santa Clara County, southeast of Los Gatos and south of South San Jose. The peak is sometimes referred to as "Mount Um" by locals. It is a well-known landmark in the Bay Area which can be recognized in Santa Clara Valley by the five-story concrete radar tower building, known locally as "The Cube" or "The Box", that sits atop the summit. The tower construction began in 1960 and completed in 1962. It supported an 85.5-ton General Electric model AN/FPS-24 long range search radar antenna "sail" used to detect incoming hostile aircraft during the Cold War.
The summit of Mount Umunhum is the site of the former Almaden Air Force Station, an early-warning radar station built in 1957 that operated from 1958 to 1980. Most of the mountain is within the Sierra Azul Open Space Preserve, managed by the Midpeninsula Regional Open Space District (MROSD).
The mountain is also the site of the Bay Area NEXRAD weather radar. The high elevation is necessary for line of sight in the region's varied terrain, but it also limits the ability to detect storms with bases lower in the atmosphere.
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- "Sierra Azul Open Space Preserve". Midpeninsula Regional Open Space District. Retrieved 2008-04-11.
- Boxer, Barbara (2009-10-20). "Opinion: It's past time for federal government to clean up Mount Um". San Jose Mercury News (San Jose, California). ISSN 0747-2099. Retrieved 2014-03-05.
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- "Almaden Air Force Station Veterans Association".
- "Umunhum Conservancy, Inc.".