For most of its history, Decatur House served as home to numerous enslaved and free African Americans who lived and worked at the site - and its architecture, in several ways, reflects the status of those residents. The two remaining original structures - the 1818 residence facing Lafayette Square and the ca. 1822 slave quarters – generally evidence the living and working conditions of enslaved men and women in urban areas as well as their owners’ desires to hide their activities from plain view.
Architect B. Henry Latrobe designed Decatur House with various access passages for a variety of different people, with the movements of enslaved people in particular tightly controlled to allow for high work efficiency but low visibility. A back stairway and an exit directly out of the kitchen onto H Street provided ways for relatively invisible movement throughout the house. Ironically, whereas the neoclassical style of Decatur House represented the egalitarian ideals of the early republic, the service spaces represented the most glaring contradiction of American democracy – the institution of slavery.
The slave quarters at Decatur House is one of only a few remaining examples of slave quarters in an urban setting, and also is uniquely significant as the only remaining physical evidence that African Americans were held in bondage within sight of the White House. Though the exact date of construction is unknown, records indicate the quarters possibly were built as a one story structure as early as September 1821 during the tenancy of the French foreign minister, as a bill for $40.40 notes iron work and a "door & frame for oven" for "back buildings," perhaps suggesting a cooking facility of some sort. Further, a January 1822 bill for more than $1300 also indicates the cost of "erecting a building joining the "house in Presidents Square."
John Gadbsy, the second owner of Decatur House, likely expanded the structure both up and out in 1836 to provide more working and living space for the large number of enslaved people – perhaps who supported his nearby National Hotel. Evidence also indicates that the first floor of the quarters served as a kitchen, laundry, and dining area for the enslaved members of the household, while the second floor served as their living quarters.
Reflecting the historical perspective of the time regarding what was considered "significant" in American history, the National Trust for Historic Preservation removed a great deal of the interior architectural fabric of the slave quarters in the 1960s to install a shop on the first floor and Trust offices on the second. However, today, the second floor in of the quarters in particular is undergoing intense investigation, and floors, windows, and chimney breasts are all being revealed and interpreted for their original intent.