Entitled: "Front of slave pen, Alexandria, Virginia" showing a Union army guard and other men in front of a building designated Price, Birch & Co., dealers in slaves, at 1315 Duke Street, Alexandria, Virginia. The Union army used the former slave jail to house Confederate prisoners. Slave Auctions were advertised when it was known that a slave ship was due to arrive. When the slave ship docked, the slaves would be taken off the ship and placed in a pen. There they would be washed and their skin covered with grease, or sometimes tar, to make them look more healthy. This was done so that they would fetch as much money as possible. They would also be branded with a hot iron to identify them as slaves. The legal institution of chattel slavery existed in the USA in the 18th and 19th centuries. Although the international slave trade was prohibited from 1808, internal slave-trading continued at a rapid pace, causing the forced migration of more than one million slaves from the Upper South to the Deep South in the antebellum years. The total slave population in the South eventually reached four million before abolition. Photographed by Andrew J. Russell, circa 1865.