The 38.6-acre campus includes twenty contributing resources. Of these resources, sixteen are buildings, generally brick with Georgian Revival or simple Colonial Revival detailing. Six of the contributing buildings date to the period between 1916 to 1942 when the complex was first developed and used as the Mount Vernon Seminary for Girls.
The remaining ten contributing buildings date from the period between 1943 and 1952 when the U.S. Naval Communications Annex (NCA) used the property for cryptographic work and continued construction in a style that complemented the existing buildings. Here, Navy crypt analysis of coded German U-boat messages helped turn the tide of the North Atlantic sea campaign during World War II.
The Mount Vernon Seminary for Girls is significant at the local level in the area of Education as the first campus developed solely for use as the Mount Vernon Seminary for Girls, the first non-sectarian female boarding school in Washington, D.C., whose curriculum was progressive for its time.
The property is significant at the national level in the area of Military for its use as the U.S. Naval Communications Annex, the site from which, during World War II, worldwide U.S. Navy cryptographic operations were directed, and where crypt-analysis of enciphered German U-boat messages and decoding of Japanese naval and merchant shipping codes took place.
The property is also significant at the local level in the area of architecture as a representative example of an educational and military campus developed with buildings reflecting the Colonial Revival and Georgian Revival styles popular in the first half of the twentieth century.
Nominated by the U.S. General Services Administration and designated May 26, 2016
National Register: August 10, 2016