The monument, dedicated in September 1866, stands atop a masonry vault containing the remains of 2,111 soldiers gathered
from the fields of Bull Run and the route to the Rappahannock.

The remains were found scattered across the battlefields or in trenches and brought here. This monument was the first memorial at Arlington to be dedicated to soldiers who had died in battle, and who later could not be identified.

Because in some instances only a few bones or a skull were recovered, it is assumed that the vault contains the remains of Confederate soldiers as well as Union troops.