Seavey's Island side of Seavey's Island at the former site of Camp Long, a stockade named for Secretary of the Navy John Long, where 1,612 prisoners of war from the Battle of Santiago de Cuba were confined from July 11 to mid-September 1898 during the Spanish–American War. Camp Heywood, a Marine camp named after Colonel Charles Heywood, was located just north of the naval prison. It was occupied after the 1st Battalion's return from Cuba in late August until September 21, 1898. According to the National Trust for Historic Preservation, the Portsmouth Naval Shipyard has 62 buildings listed on the National Register
Battle of Santiago de Cuba attack the largely undefended East Coast while the fleet sailed about in an effort to engage him, prey upon American shipping, or perhaps sail up the Potomac and set fire to Washington, D.C. Ultimately, Cervera did none of these, managing to evade the U.S. fleet for several weeks, confounding his American counterparts, and re-coaling in the process before finally seeking refuge in the harbor of Santiago de Cuba. On May 29, 1898, an American squadron sighted Cervera's newest ship, the cruiser , and immediately established a blockade around the mouth of the harbor. The Spanish soon found themselves "blockaded closely