Mount Umunhum

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Mount Umunhum
Mount Umunhum from the northeast
Highest point
Elevation 3,489 ft (1,063 m)  NAVD 88[1]
Prominence 586 ft (179 m) [1]
Coordinates 37°09′38″N 121°53′55″W / 37.1605016°N 121.8985666°W / 37.1605016; -121.8985666Coordinates: 37°09′38″N 121°53′55″W / 37.1605016°N 121.8985666°W / 37.1605016; -121.8985666[2]
Location Santa Clara County, California, United States
Parent 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)[3] 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.[4] 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"[5] 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.

Mount Umunhum is dusted with snow a few times a year.

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.[6] Most of the mountain is within the Sierra Azul Open Space Preserve, managed by the Midpeninsula Regional Open Space District (MROSD).

The summit is closed to the public due to hazardous materials and unsafe partially demolished structures of the former Air Force station.[7]

Plans are underway to clean up and restore the summit for public use, with restoration or demolition of the landmark tower being considered.[8][9]

The mountain is also the site of the Bay Area NEXRAD weather radar.[10] 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.

On May 10, 2016, the Santa Clara County Board of Supervisors voted unanimously to list the Almaden AFS AN/FPS-24 Radar Tower on the County Heritage Resource Inventory, thus giving it official historic status and demolition protection.[11]


  1. ^ a b "Mount Umunhum, California". 
  2. ^ "Mount Umunhum". Geographic Names Information System. United States Geological Survey. 
  3. ^ "Sierra Azul Open Space Preserve". Midpeninsula Regional Open Space District. Retrieved 2008-04-11. 
  4. ^ 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. 
  5. ^ Rogers, Paul (May 29, 2009). "Stalled plans for park on 'Mount Um' gaining ground". San Jose Mercury News. Retrieved March 1, 2012. 
  6. ^ "Almaden AFS, CA Site History". Radar Museum. Air Defense Radar Veterans Association. Retrieved February 27, 2012. 
  7. ^ "Mt. Umunhum Notice of Area Closures" (PDF). Midpeninsula Regional Open Space District. Retrieved 2012-03-01. 
  8. ^ "Mt. Umunhum Conservancy". Retrieved 2013-07-02. 
  9. ^ "Mt. Umunhum Cleanup and Restoration". Midpeninsula Regional Open Space District. Retrieved 2010-12-20. 
  10. ^ "NOAA Agencies Partner with the Private Sector" (PDF). National Oceanic and Atmospheric Administration. 
  11. ^ "Mount Umunhum cube to stay: Cold War relic gets historic designation". San Jose Mercury News. 10 May 2016. Retrieved 23 May 2016. 

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