The first-ever wreckage of a ship that went down with slaves on board has been found just 100 yards off the coast of South Africa where it sank in 1794. The Portuguese ship, Sao Jose-Paquete de Africa, set out from Mozambique Island with more than 400 slaves shackled in its hold in December of that year, bound for Brazil's sugar plantations, but it fell well short of the 7,000-mile journey, the New York Times reports. As the ship rounded the Cape of Good Hope 24 days into the four-month trip, stormy waters broke it up on reefs off Cape Town. Though the captain and crew escaped—and sent about half the slaves to shore, where they were sold two days later—212 slaves died at sea. In the 1980s, treasure hunters identified the shipwreck as a Dutch merchant vessel that sank in 1756. Two decades later, researchers who'd been searching for a slave ship for a decade uncovered clues that revealed a much more significant find.
Believing its copper fastenings and sheathing suggested a late-18th-century ship, archaeologist Jaco Boshoff began combing records, eventually finding a document from the inquest of the Sao Jose's captain. It described a slave ship that went down at the exact location the apparent Dutch ship had been found. The ship's manifest also noted the vessel set out from Lisbon with 1,500 iron blocks as ballast—a "signature for slaving," a historian says—used to offset the weight of living cargo. Dives to the wreck turned up encrusted shackles, but the final piece of the puzzle came in 2012, when divers found black iron bars buried in the sand. "I knew immediately," Boshoff says. A memorial will be held tomorrow with soil from Mozambique Island deposited on the wreck, before artifacts are sent to the National Museum of African American History and Culture, opening in DC next year, on a 10-year loan, Smithsonian reports. (A Finnish shipwreck could hold $56 million in coins.)