Mississippi Sound, arm of the Gulf of Mexico, c.100 mi (160 km) long and from 7 to 15 mi (11–24 km) wide, extending from Lake Borgne in Louisiana on the west to Mobile Bay in Alabama on the east. It is part of the Intracoastal Waterway and is separated from the Gulf by a series of narrow islands and sandbars. Cat, Horn, Petit Bois, and Dauphin are the main islands. Gulfport, Biloxi, and Pascagoula, Miss., are on the Mississippi Sound.
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