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
Siege of Santiago along San Juan Heights. In the charge at the Battle of San Juan Hill U.S. forces captured the Spanish position. At the Battle of El Caney the same day, U.S. forces took the fortified Spanish position and were then able to extend the U.S. flank on San Juan Hill. The destruction of the Spanish fleet at the Battle of Santiago de Cuba allowed U.S. forces to safely besiege the city. On July 3, 1898, the same day as the naval battle, Major General William "Pecos Bill" Shafter began the siege of Santiago. Shafter fortified his position on San Juan Heights.