The American Tract Society Building, located at the southeast corner of Nassau and Spruce Streets, was constructed in 1894-95 to the design of architect R. H. Robertson, who was known for his churches and institutional and office buildings. It is one of the earliest extant steel skeletal-frame skyscrapers in New York partially of curtain-wall construction. This was also one of the city’s tallest and largest skyscrapers upon its completion. Twenty full stories high and clad in rusticated gray granite, with gray Roman brick, and buff-colored terra cotta, the building was constructed with a U shaped plan, having an exterior light court. A three-story arcade, open at the top story and with winged angels at the upper corners, surmounts the western half of the building; a three-story hipped roof tower rises through the arcade.
Old Structures Engineering (OSE) was retained by the building’s owners as the project manager and structural engineers to oversee the work addressing the advanced state of deterioration of the four terra cotta angels that had been strapped back to the building to prevent pieces of terra cotta from falling to the street. The work included the replication of four angels in terra cotta and fabrication of gilded globes that surmount the angels heads. OSE designed repairs to the back-up masonry, and designed a new, concealed, armature system to which the new terra cotta units could be anchored. OSE coordinated the efforts of the team with the Landmarks process and the needs of the building occupants.