Serpentine shell middens, perhaps 1500 years old, attest to at least seasonal occupation by the Native American Mound Builder culture. Shell Mound Park, along the Island's northern shore, is administered by Alabama Marine Resources Division.
In 1519, the Spanish explorer Alonzo Pineda was the first documented European to visit, staying long enough to map the Island with remarkable accuracy.
The Island's French history began when the explorer Pierre Le Moyne, sieur d'Iberville, virtually the founder of French Louisiana, arrived at Mobile Bay, 31 January 1699, and anchored near the island. on his way to explore the mouth of the Mississippi River. The first permanent settlement on the island, called "Massacre Isle" for heaps of skulls that had been found there, was a trading depot, unloading goods from Santo Domingo and France, and collecting furs in a short-lived fur trade. Mobile Bay itself, before it was dredged, was too shallow, and its sand bars too shifting and treacherous, for ocean-going vessels. Renamed for Louis XIV's great-grandson and heir, the Dauphin, in 1712, and fortified, the island retained its strategic importance, even after the administrative capital of Louisiana was removed from the fort at Mobile Bay in 1721. Dauphin Island was captured by the British in 1766 during the Seven Years War, but retaken by the Spanish in 1780 during the American Revolutionary War. During the War of 1812, American forces captured the island (1813) to prevent British forces from using it.
Fort Gaines on the eastern tip of the island was built in 1821-1848. Occupied by Confederate forces in 1861, the fort was captured by Federal troops during the Battle of Mobile Bay. The phrase, "Damn the torpedoes, full speed ahead," was spoken by U. S. Admiral David Farragut just a few hundred yards from Dauphin Island's shore.
The first Sand Island Lighthouse, authorized in 1834, was replaced by a structure 150 feet high, at a cost of $35,000, that was dynamited by Confederate forces. The present lighthouse (1873; in use until 1970), now belongs to the Department of Interior and has been placed on the National Register of Historic Places.
In the 18th and 19th century the few hundred inhabitants were self-sufficient fishermen and oystermen. From the early 20th century hotel and ferry services encouraged development, all but swept away in Hurrican Frederic, 1979. The island today is home to a marine sciences laboratory, The Estuarium, and numerous private homes. Beaches attract some tourism, and fishing is a popular activity in the waters around the island.
There is also a bird sanctuary; Dauphin Island is the first landfall encountered by many birds as they migrate north from South America, and as a consequence many species can be found resting there before continuing their journey.
A bridge connecting the island to the mainland across Dauphin Island Sound was built in the 1950s; it was destroyed by Hurricane Frederic but was rebuilt.
Dauphin Island is also the name of the incorporated community (Town of Dauphin Island, Alabama) that is situated on the island. The Island has a permanent population of about 1,200.