The Civil War Unknowns Monument is located on the grounds of Arlington House. This site was once a grove of trees near one of the estate’s flower gardens. The 12-foot high granite cenotaph sits atop a burial vault that contains the bodies of 2,111 unidentified soldiers. Historians believe that the vault contains Union and Confederate dead because it was difficult to identify the remains collected from battlefields near Bull Run and the Rappahannock.
The original 1865 monument was based on a design by Quartermaster General Montgomery Meigs. The outward appearance of the monument has changed over the years. The Rodman guns and pyramidal stacks of cannon balls that once adorned the top of the monument are now located beside the base. The redesigned top is inspired by the description of the Ark of the Covenant found in the Book of Exodus. A series of three stone and granite slab bases were installed to lift the monument off the ground. The side of the monument has an inscription venerating those who are buried in the vault below. It was the first monument dedicated to soldiers who died in battle whose remains could not be identified. This monument was the focus of Memorial Day ceremonies in Arlington Cemetery until the construction of the Tomb of the Unknowns in 1921.