The island's name may come from its shape - a long narrow strip tapering to a western point - or from the cattle that early French colonists put ashore here. In 1718, Antoine-Simon Le Page du Pratz arrived in Louisiana and later wrote about Horn Island in his History of Louisiana. The first Canadians who settled on nearby Dauphin Island had placed their cattle on Horn Island in great numbers, he recorded, 'whereby they came to grow rich even when they slept.' The animals required no tending on the isolated island, multiplying freely until their owners harvested the profits. It was an early experiment in hands-off ranching, made possible by the same isolation that defines the island today. The cattle are long gone, but the wildness they grazed in has endured.

Horn Island stretches several miles east to west but barely reaches a mile at its widest. The southern shore faces the open Gulf of Mexico with long beaches of sugar-white sand. The northern side shelters Mississippi Sound. Between the two coasts, the island holds a surprising interior: freshwater lagoons ringed by saw palmettos, small groves of tall pines, dunes crowned with sea oats. Alligators patrol the lagoons. Ospreys, pelicans, anhingas, ibises, herons, and terns nest along the shores. Manatees pass through the surrounding waters. The island is part of the Gulf Islands National Seashore, protected as wilderness and accessible only by private boat - there is no ferry service, no dock, no road. Visitors who make the crossing find a landscape that looks much as it did when Le Page du Pratz first described it three centuries ago.

Between 1943 and 1945, Horn Island took on a darker role. The U.S. Army closed the island to all public access and used it as a biological weapons testing site. The remote, uninhabited barrier island offered ideal conditions for testing agents that could not safely be released near populated areas. Details of the program remained classified for decades. The testing ended with World War II, and the island eventually returned to its natural state, but the episode adds an unsettling layer to what otherwise seems like untouched paradise. The Army's interest in Horn Island, like the French colonists' interest before it, came down to the same quality: isolation.

In 1989, Horn Island entered a different kind of experiment. The U.S. Fish and Wildlife Service selected it as a propagation site for the endangered red wolf, hoping the island's isolation would allow a captive population to breed without the threats found on the mainland. For nine years, red wolves roamed the same dunes and pine groves where Anderson had painted and the Army had tested weapons. The program ended in 1998 when officials determined that increasing human visits created too great a likelihood of wolf-human encounters. The wolves were removed, and Horn Island returned to its birds, alligators, and silence. The island sits in a chain of Mississippi-Alabama barrier islands - Petit Bois and Dauphin to the east, Ship Island and Cat Island to the west - each with its own character, but none as wild as Horn.