The Old Post Office Historic Vault

During the complete renovation of the Old Post Office Building at 1100 Pennsylvania Avenue, NW, a remarkable historic artifact was rediscovered: a long-forgotten steel vault door concealed beneath decades of over-painting in the building’s basement. Investigations revealed that beneath more than a century of accumulated paint lay an exquisitely decorated surface, complete with gilded moldings and a richly colored Great Seal of the United States—still intact.

Our conservation team undertook a meticulous, multi-stage treatment to preserve and reveal this extraordinary find. More than 100 years of non-original overpaint were carefully removed using controlled methods to avoid disturbing the original decorative finish. A discolored varnish layer, which had significantly altered the appearance of the surface, was then reduced to recover the original color balance and clarity of the design. Areas of paint loss on the Seal and exposed metal were sensitively in-painted to restore visual continuity, while ensuring all interventions remained reversible and historically appropriate. Finally, the original paint—now stable and fully visible—was sealed beneath a conservation-grade lacquer to protect it for future generations.

Constructed between 1892 and 1899, the Old Post Office Building is one of Washington, DC’s most significant architectural landmarks. The rediscovered vault door now stands as a rare and tangible surviving detail from the building’s original use, offering insight into the craftsmanship, symbolism, and security measures of a major federal facility at the turn of the 20th century.