St. Joseph Island Light stood at the entrance to Lake Borgne on the north side of Mississippi Sound, helping guide navigation along a low, shifting Mississippi coast. Its importance came from the need for a fixed signal in an unstable landscape, yet erosion steadily made St. Joseph Island itself a poor location for the lighthouse. As the island wore away, the light was replaced by Lake Borgne Light farther west. A hurricane destroyed the original structure in 1893, and an unmanned light and a USGS water monitoring station were later placed on the ruins, underscoring the Gulf Coast’s constant exposure and changeability.