In 1991, exploratory work on a new federal building in Lower Manhattan uncovered more than 400 caskets in an unmarked cemetery. It turned out to be a former six-acre burial ground dating back to the mid-1630s—the oldest and largest of its kind in North America for both enslaved and free Africans. (An estimated 15,000 people were buried here.) The site now features a memorial, public art, and a visitor’s center that delves into the history of slavery and role of Africans in early New York.