Sand Island Light, off Dauphin Island at the mouth of Mobile Bay, marks Alabama’s southernmost point and has long stood as a major Gulf Coast navigational landmark. First established in the late 1830s, the lighthouse was replaced in 1859, then destroyed during the Civil War after Union troops used it to observe Fort Morgan. The present tower dates from September 1864 and was built on an unusually massive foundation to withstand the shifting site. Over time, erosion consumed Sand Island, leaving the lighthouse surrounded by water. Repeated storms and failed stabilization efforts have made it one of the nation’s most endangered lighthouses, though preservation work continues.