There is a detailed plain text history posted at Naval Security Group Station History Below is an excerpt:
In July 1922, the U.S. Navy formally established a cryptologic element, known as the Communication Security Unit, or DNC OP-20-G; a part of the Office of the Director of Naval Communications. The unit was located at the Main Navy Building, commonly referred to as
“Main Navy”, 18th St. & Constitution Ave.
In October, 1928, the Navy also established a school for enlisted Navy and Marine Corps intercept operators at the Navy Department in Washington, D.C. In a specially constructed blockhouse, a classroom and eight intercept positions were erected on the roof of “Main Navy”;
probably as much for the sake of privacy as for the lack of space. Student graduates became known as the “On the Roof Gang.” The first instructor was Chief Radioman Harry Kidder, who had taught himself to recognize and intercept Japanese radio communications, while previously
serving in the Philippines.
On March 11, 1935, the unit was redesignated as the Communications Security Group (CSG). This date is observed as the birth of the Naval Security Group. In February, 1943, the CSG transferred to a new facility at 3801 Nebraska Ave. NW, Washington, DC. The facility at 3801 Nebraska Avenue was known as the Communications Supplementary Annex from February, 1943. It was renamed NAVCOMMSTA Washington (NCSW) on July 7, 1948, and redesignated as the Naval Security Station (NAVSECSTA) on September 21, 1950.
25 May 1945, at the Naval Communications Annex, 3801 Nebraska Ave., Washington DC
