Much of the land that is now the National Mall was once occupied by large Maryland plantations which relied on the labor of enslaved Africans to cultivate tobacco. Even after this land became part of Washington, D.C., it continued to serve the slave trade until Congress abolished the practice within the District in 1850.

Addressing the House of Representatives on February 23, 1849, Horace Man, a member of the Free Soil Party from Massachusetts, described the landscape that is now the Mall, “from the western front of this Capitol . . . as you cast your eye along the horizon and over the conspicuous objects of the landscape—the President's mansion, the Smithsonian Institution, and the site of the Washington Monument—you cannot fail to see the horrid and black receptacles where human beings are penned like cattle, and kept like cattle that they may be sold like cattle.”