Fort Stark was a military fortification in New Castle, New Hampshire. Located at Jerry's Point on the southeastern tip of New Castle Island, most of the fort was developed in the early 20th century, following the Spanish-American War, although there is evidence of earlier earthworks on the site. The purpose of Fort Stark was to defend the harbor of nearby Portsmouth and its vital United States Navy facilities. The fort remained in active use through the Second World War, after which it was used for reserve training by the Navy. The property was turned over to the state of New Hampshire in 1979, which established Fort Stark Historic Site. The grounds are open to the public during daylight hours.