Mare Island Naval Shipyard, Administrative Offices, Walnut Avenue, east side between Seventh & Eighth Streets, Vallejo, Solano County, CA

Significance: Building 521 is a contributing element of the Mare Island Historic District. Building 521 is significant historically and architecturally. Historically, the building is important as the administrative hub of Mare Island during World War II and the Cold War. Architecturally, it is important as the most successful Modern building at the base. While there are many modern buildings there, Building 521 succeeds by paying homage to nearby Building 47, while establishing its own separate identity as an easily identifiably work of the early 1940s.
Survey number: HABS CA-1543-Q
National Register of Historic Places NRIS Number: 75002103