Horn Island (Gulf Islands National Seashore, NPS)

Horn Island is the barrier island that tested weapons the mainland couldn't know about. From October 1943 to July 1944, the Army's Chemical Warfare Service ran a quarantine station on the island ten miles off Pascagoula — roughly two hundred scientists and technicians, a state-of-the-art necropsy facility, animal holding pens, and a 7.6-mile narrow-gauge railway hauling equipment across the sand to the test grid. The island was picked for isolation; the catch was discovered late — for two-thirds of the year the prevailing wind blew toward the populated coast.

The twenty-three tests were, by the record, a failure — bombs filled with botulinum toxin detonated over grids of caged guinea pigs failed to disperse the agent, and the animals lived. The station closed, the equipment went to Camp Detrick, and the island's second toxic chapter followed: in 1946-47, Operation Hornblow burned more than 130 leaking captured German mustard-gas bombs in shallow trenches — ruptured with rifle fire, ignited with oil-soaked rags, the empty casings barged out and dumped at sea.

Before and after the Army, the island kept its quieter records — the powder horn a French sailor lost in the 1600s that named it, the lighthouse keeper Nelson and his family lost when the 1906 hurricane blew the light away, and in the 1950s the painter Walter Anderson, who rowed out alone to live among the dunes and made Horn Island his great subject. The wilderness designation protects the whole strange record — the dunes where the test grid ran, the shore where the keeper wouldn't leave, and the emptiness Anderson crossed to paint.

Horn Island is the archive's quarantine file — the Mississippi barrier island where the Army ran a secret chemical-warfare station in 1943-44 and burned captured German mustard bombs in 1946, between the lighthouse the hurricane took and the wilderness Walter Anderson painted.