[2] The Marine hospital was a three-story building built of brick with an I-shaped footprint; a fourth story was added in 1866.

[2] Two buildings on the site were built in the early 19th century to handle ordnance for the United States Navy.

The buildings were built by the Bureau of Ordnance and the land was transferred back to the hospital in 1910.

[2] The larger building was designed to securely store explosives and ordnance and was not intended for human occupancy.

The ceilings are made of brick and include vaults which were designed to contain fire and force explosions upward rather than outward.