Dauphin Island is a town in Mobile County, Alabama (U.S.), on a barrier island also named Dauphin Island, at the Gulf of Mexico.The Gulf of Mexico is to the south of the island the Mississippi Sound and Mobile Bay are to the north. The island eastern end helps to define the mouth of Mobile Bay. The eastern, wider portion of the island, is shaded by thick stands of pine trees, but the narrow, western part of the island features scrub growth and few trees.Dauphin Island is home to Fort Gaines, Dauphin Island Sea Lab, The Estuarium public aquarium, the Dauphin Island Airport, boat ramps, a large public pier, historics sites, several restaurants, new condominium developments, and numerous private homes. Beaches attract tourism, and fishing is a popular activity in the waters around the island. The island is connected to the mainland by the Gordon Persons Bridge.