As described in the Mount Vernon Seminary National Register Nomination, “From January 1943 until the surrender of Germany in May 1945, the Mount Vernon Seminary for Girls served as the Naval Communications Annex (NCA), the site of U.S. Naval cryptanalysis of coded German U-boat messages during World War II. The NCA utilized the most up-to-date cryptanalytic technology, particularly through the use of four-rotor American bombes, all of which were housed at the NCA. The information decoded and translated at the NCA significantly reduced Allied losses to German U-boats and greatly increased the number of U-boats destroyed during the latter-half of World War II. The cryptanalytic efforts undertaken at the NCA aided in “turning the tide” of the North Atlantic sea war during World War II and consequently aided in the May 1945 surrender of Germany and reduced the loss of Allied productivity and lives from 1943 through May 1945. After the war and until 1952, the NCA remained the center for U.S. Naval cryptanalysis for the Atlantic region as the focus changed to the Cold War.”
“The facility was the center for many activities undertaken by the U.S. Navy, the most important of which was the recovery of keys of the German primary cipher system deciphered by the American bombe. By 1945, 121 bombes occupied the two floors of Building 4, all of them operated by over six hundred WAVES. [WAVES is the acronym of Women Accepted for Volunteer Emergency Service, the U.S. Navy’s corps of female members.] Banks of bombes operated twenty-four hours a day, seven days a week at the facility. These machines helped greatly to speed the reading of German Enigma-coded U-boat messages. By May 1944, American bombes routinely broke U-boat messages. The average delay in breaking the daily key settings was only twelve hours. Consequently, the U.S. Navy could read all of the Atlantic U-boat messages sent in the latter half of the day at the same time as the Germans.”
“The WAVES who operated the machines were housed at Quarters ―D, a complex of thirty buildings situated on forty acres of land located across Nebraska Avenue, to the west of the NCA. At its peak, the Quarters D complex, the largest WAVES barracks in the United States, housed 3,700 women.”
They WAVES were college educated women, who were recruited by the Navy, many from the Seven Sister colleges. They were sworn to secrecy and told never to tell their stories. Many were recruited to Washington, DC, without knowing what it was they were going to do. Seniors at the Seven Sisters were secretly invited to meetings with their math or astronomy professors who asked: Do you like crossword puzzles and are you engaged to be married?
Information from the Mount Vernon Seminary National Register Nomination, prepared by Emma Young/ Architectural Historian; later edits by Elizabeth Hannold, GSA, Center for Historic Buildings.
Additional reference: Code Girls by Liza Mundy