On April 22, 1865, the eighth day of the manhunt across southern Maryland for President Lincoln’s assassin, John Wilkes Booth, U.S. Army and Navy detachments were searching the region, including vessels of the Potomac Flotilla that had helped protect Washington, D.C., from Confederate naval attack during the previous four years. That day, the Quartermaster Depot in Washington ordered the propeller-driven coal barge Black Diamond to join the flotilla. Its eleven-man crew took it from Alexandria, Virginia, to Piney Point, Maryland, for instructions and then headed back up the Potomac River. At 12:35 A.M. on April 23, they anchored for the night within a mile of the Blackistone Island Lighthouse. Meanwhile, the 308-ton sidewheel steamer Massachusetts, also named John W.D. Pentz, was traveling downriver toward Black Diamond on its way to Fort Monroe, Virginia, carrying 300 Federal soldiers recently released from Northern convalescent hospitals. Shortly before 1 A.M., Massachusetts struck Black Diamond on the port side just behind the wheelhouse, tearing open the barge’s iron hull to the waterline and crushing the steamer’s bow to the waterline as well. The captain ordered everyone to jump from Massachusetts onto Black Diamond, and about half the men did so, which inadvertently helped sink the much smaller vessel. In the end, 87 men drowned, including 7 of the 11 aboard Black Diamond. Massachusetts was soon repaired and returned to service.