The Harbor Defenses of Long Island Sound was a United States Army Coast Artillery Corps harbor defense command.
 It coordinated the coast defenses of Long Island Sound and Connecticut from 1895 to 1950, beginning with the Endicott program.
 These included both coast artillery forts (all but two on islands in the sound) and underwater minefields.
 The area defended included the approach via the Sound to New York City, the port cities and manufacturing centers of New London, New Haven, and Bridgeport, and eventually included the submarine base and shipyard in Groton.
 The command originated circa 1900 as an Artillery District, was renamed Coast Defenses of Long Island Sound in 1913, and again renamed Harbor Defenses of Long Island Sound in 1925.
Long Island Sound is a tidal estuary of the Atlantic Ocean, lying between the eastern shores of Bronx County, New York City, southern Westchester County, and Connecticut to the north, and the North Shore of Long Island, to the south.
 From east to west, the sound stretches 110 miles (177 km) from the East River in New York City, along the North Shore of Long Island, to Block Island Sound.
 A mix of freshwater from tributaries and saltwater from the ocean, Long Island Sound is 21 miles (34 km) at its widest point and varies in depth from 65 to .
Fort H. G. Wright was a United States military installation on Fishers Island in the town of Southold, New York, just two miles off the coast of southeastern Connecticut, but technically in New York.
 It was part of the Harbor Defenses of Long Island Sound, along with Fort Terry, Fort Michie, and (in World War II) Camp Hero.
 These forts defended the eastern entrance of Long Island Sound and thus Connecticut's ports and the north shore of Long Island.
 The fort was named for Union General Horatio G. Wright, a former Chief of Engineers who was born in Clinton, Connecticut.
Fort Michie was a United States Army coastal defense site on Great Gull Island, New York.
 Along with Fort H. G. Wright, Fort Terry, and Camp Hero, it defended the eastern entrance to Long Island Sound as part of the Harbor Defenses of Long Island Sound, thus defending Connecticut's ports and the north shore of Long Island.
The 11th Coast Artillery was a coast artillery regiment in the United States Army, first constituted in the Regular Army on 27 February 1924.
 It primarily served as the Regular Army component of the Harbor Defenses of Long Island Sound (HD Long Island Sound), New York from 1924 through 1944, when it was relieved and disbanded as part of an Army-wide reorganization.
Fishers Island is located at the eastern end of Long Island Sound, 2 mi off the southeastern coast of Connecticut across Fishers Island Sound, about 9 mi long and 1 mi wide.
 It is about 11 mi from the tip of Long Island at Orient Point, 2 mi from Napatree Point at the southwestern tip of Rhode Island and from Groton Long Point in Connecticut, and about 7 mi southeast of New London, Connecticut, from which it is accessible by plane or regular ferry service.
Little Gull Island is a small island in Long Island Sound, located approximately 0.4 mi northeast of Great Gull Island.
 Both islands are located in the Town of Southold, in Suffolk County, New York, and lie roughly midway between Plum Island and Fishers Island.
 Little Gull Island is approximately 4.6 mi southwest of Fishers Island and the channel of water between them is the main entrance to Long Island Sound, known as "The Race".
Race Rock Light is a lighthouse on Race Rock Reef, southwest of Fishers Island, New York.
 The reef is a dangerous set of rocks off the coast of Fishers Island on Long Island Sound and was the site of many shipwrecks.
 It is currently owned and maintained by the New London Maritime Society as part of the National Historic Lighthouse Preservation Act program.
The Watch Hill Lighthouse in Watch Hill, Rhode Island has served as a nautical beacon for ships since 1745, when the Rhode Island colonial government erected a watchtower and beacon during the French and Indian War and Revolutionary War.
 The original structure was destroyed in a 1781 storm, and plans were discussed to build a new lighthouse to mark the eastern entrance to Fishers Island Sound and to warn mariners of a dangerous reef southwest of Watch Hill.
Glacial Lake Connecticut formed over what is now Long Island Sound and coastal Connecticut at the fore edge of the ice sheet of the Wisconsin glaciation, as the lobe of the Laurentide ice sheet began to retreat, some 18 to 20,000 years before present.
 It was dammed by the terminal moraine that now forms the spine of Long Island and Fishers Island.
 About 15,000 BP, the moraine dam that impounded Lake Connecticut failed; the outlet, known as The Race for its tidal rip currents, lies between the North Fork of Long Island and Fishers Island.
 For a time, much of the lake bed was exposed to wind-driven erosion: the cue is found in soundings that reveal regional unconformities in the sediment bed of Long Island Sound.

Question: What military installation that defended the eastern entrance to Long Island Sound as part of the Harbor Defenses of Long Island Sound is on Fishers Island?
Answer: Fort H. G. Wright