Uncovering the sad truth of the past, Slave Pens existed in and around all of Washington in the 1860s. This photo shows one of those in Alexandria during the 1860s. Learn more at the Library of Congress.

This week marks the 152nd anniversary of the D.C. Emancipation Act, which ended slavery in the District of Columbia and ultimately freed almost 3,000 slaves in Washington. Celebrate with a parade and other events, and read the transcript of the bill here.

Take a look at this fascinating old broadside condemning the sale and keeping of slaves in the District of Columbia during the 1835-36 petition campaign. Learn more about this powerful piece of abolitionist history and its arguments for freedom.

Learn about taxes, regulations and more from Washington in 1840 with this article. We explore regulation of slaves, guns, gambling, and more in this fascinating look into life in the city before emancipation.