Fort Mansfield and similar forts stretching from Galveston to Maine can be traced back to a joint Army-Navy Board created in 1883 known as the Gun Foundry Board. Its report a year later warned of the defenseless condition of the USA's coasts and recommended a system of fortifications to protect harbors and coastal cities from invasion. In 1885 this Board was replaced by what has become known as the Endicott Board which in 1886 issued formal recommendations for a major coastal defense network. Fort Mansfield was one of numerous coastal artillery installations constructed to guard the eastern entrance to Long Island Sound as part of the coastal defense network for New York City. It was named in honor of Joseph K. Mansfield (1803–1862) who had served as Chief Engineer Of The Army during the Mexican War and was eventually promoted to Inspector General Of The Army.
In 1898 the United States government purchased 60 acres (240,000 m2) on Napatree Point, a long, narrow spit of land jutting out from Watch Hill. The fort was located on a bend in the spit beyond which was called Sandy Point. Construction of the fort began the following year. When the fort was first manned in 1901 it was considered a sub-post of Fort Trumbull in New London, Connecticut. But when the fort was fully manned in 1902 its status changed to an independent battery. The fort’s main armaments consisted of two Crozier 8-inch (200 mm) disappearing guns plus several rapid-fire 5-inch (130 mm) cannon and were divided among three batteries: Wooster, Crawford, and Connell.
War games held in 1907 proved the fort had a fatal flaw. Any attacking vessel could approach Fort Mansfield from a “dead angle” along the Rhode Island coast which its long-range 8 inch cannon, did not cover. The installation could be bombarded with impunity and depending on where an invading party landed, it could assault the fort opposed by nothing better than small-arms fire. A report on the war games stated "... I believe I could capture Ft. Mansfield with a fleet of coal barges, equipped with 6-inch rapid fire guns".
Because of this fatal design flaw, the fort was removed from the list of active coastal artillery posts in 1909. By 1911 only 18 men were left to man the post. That dropped to six men in 1916 and that small contingent remained until 1926 when the government placed the land up for sale. With one developer proposing nearby land on Sandy Point to be divided up into some 674 plots, the land was purchased by a private syndicate eager to prevent the land from being used for “cheap little houses” that might affect the exclusive character of Watch Hill. The sale was finalized in 1928.
All the government buildings were demolished during the winter of 1928–29 leaving the three concrete gun emplacements behind. Batteries Wooster and Crawford, while overgrown, survive to this day but Battery Connell has succumbed to sea erosion which has pushed the beach back some 200 feet (61 m) since the fort was built. What remains of Connell can sometimes be seen at low tide.
In August 2009, a small group of young adults interested in historical preservation began a cleanup project on Fort Mansfield. Finding roots to be the major source of cracks and deterioration, foliage was cut back. The fort's decay has slowed because of the lack of the roots' pressure against the structure.
While this project proved beneficial in alleviating some of the stresses upon the fort, efforts from the community must occur to maintain the integrity of the constructions.In 2011, the Watch Hill Fire Department placed railings along the top edges of the main building to prevent people from enjoying and exploring the fort. They also placed steel covers blocking the steps to prevent tourists from accessing the lower level of the site. These barriers are, however, easily circumvented by even casual visitors. Many of them have already been vandalized and destroyed.
- Michael Carroll(Founder of the New England Spiritual Team)
- "Fort Mansfield" by Clement A. Griscom, 1984. Sponsored by the Westerly Historical Society
- Aerial view of the ruins of Fort Mansfield at Google Maps