Nebraska Avenue Complex

Nebraska Avenue Complex (also called NAC) was former headquarters of Mount Vernon Seminary and OP-20-G. Currently it houses the United States Department of Homeland Security.

Between 1917 and 1942 complex housed Mount Vernon Seminary. By the end of 1942 United States Department of the Navy took over the buildings and formally acquired the land for $1.1 million US dollars on July 20, 1943. After acquirement area has been renamed to Communications Supplementary Annex.

Between February 1943 and July 1946 Annex housed Communication Security Section, which was relocated from the Main Navy Department building in Washington, D.C. It changed to Navy Communications Station (also known as NAVCOMMSTA Washington (NCSW)) in July 7, 1948, and redesignated as the Naval Security Station (NAVSECSTA) in September 21, 1950. Between June 1943 and December 1949 Annex also housed Naval Code and Signals Laboratory.

In September 1950, the Communications Security Group and the Communications Supplementary Activity Washington, merged to officially form the establishment of the Naval Security Group, headquartered at NAVSECSTA. From 1951 Station housed Armed Forces Security Agency units and after creation of the National Security Agency in 1952, Station housed NSA headquarters and Security Branch, Naval Communications Division.

In 1956 NSA Security Branch, Naval Communications Division was redesigned into Naval Security Group Headquarters Activity. By 1961 it changed to Naval Security Group Headquarters, Washington D.C. and in 1968 – to Naval Security Group Command, Washington D.C. Since 1971 it was redesigned as Naval Security Group Command Headquarters.

The Communication Security Group (COMNAVSECGRU) headquarters staff officially moved from NAVSECSTA to Fort George G. Meade in November 1995.

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