Constructing a Stockade in Alexandria

Black laborers wield shovels and pickaxes as they dig a trench in front of a newly built stockade in Alexandria during the Civil War. In the middle distance, at right, white officials (one of whom is seated and holding a squirming dog that appears out of focus) oversee the work. Since the city was occupied by federal troops during the war, refugees from slavery fled there to achieve freedom, and many of them became paid laborers for the U.S. Army.