About this Unit
Naval Security Group Activity (NSGA) Skaggs Island was a United States Navy installation located near Vallejo, California, operational from 1942 to 1993. Originally established during World War II as a radio intelligence and direction-finding station, its primary mission was signals intelligence (SIGINT) collection and cryptologic operations throughout the Cold War. NSGA Skaggs Island played a vital role in monitoring and intercepting communications of potential adversaries, supporting national defense and fleet operations across the Pacific. The station was decommissioned in 1993 as part of broader post-Cold War military restructuring, and the property was later transferred to the U.S. Fish and Wildlife Service.
Historical Facts
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Secretive Mission: NSGA Skaggs Island (Naval Security Group Activity) was a top-secret U.S. Navy communications and intelligence station, primarily focused on signals intelligence (SIGINT) during the Cold War.
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Location: The base was situated on Skaggs Island, a reclaimed marshland near Vallejo and Napa, California, surrounded by wetlands and levees—isolating it from civilians.
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Origins: The site was originally built as a radio receiving station in 1942, supporting World War II efforts to monitor and intercept enemy communications.
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Wullenweber Antenna: NSGA Skaggs Island was famous for its massive circular Wullenweber antenna array (AN/FRD-10), dubbed the “Elephant Cage,” which could intercept radio transmissions from thousands of miles away.
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Cold War Significance: The unit played a crucial role in gathering intelligence on Soviet and other foreign military communications, contributing to national security throughout the Cold War.
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Women in Uniform: In the 1970s and 1980s, the base was notable for integrating women into its intelligence operations, reflecting changing roles in military service.
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Decommissioning: NSGA Skaggs Island was officially closed in 1993 as part of post-Cold War military downsizing, ending over 50 years of secretive operations.
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Environmental Transition: After closure, the land was transferred to the U.S. Fish and Wildlife Service and is now part of the San Pablo Bay National Wildlife Refuge, supporting habitat restoration.
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Urban Legends: Due to its mysterious nature and restricted access, the base inspired local rumors and urban legends about underground tunnels and secret experiments.
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Preserved Legacy: While most buildings have been demolished, the site’s legacy is preserved through oral histories, veteran reunions, and historical markers commemorating its vital role in U.S. military intelligence.
