Fort Gaines went up at Dauphin Island's eastern tip starting in 1821, built to command the entrance to Mobile Bay. The engineers who designed it solved a problem every garrison commander faced: sanitation for approximately 400 soldiers, in a coastal fort with no running water. Their answer was the tidal latrine — one of the earliest of its kind in American military construction. Twice daily, on incoming and outgoing tides, Mobile Bay flushed the system automatically, routing waste directly to the bay with no manual maintenance required. Soldiers reached it through a tunnel running beneath the gun platforms and earthworks. The same coastal position that made Fort Gaines strategically essential — sitting at the mouth of the bay, commanding the water — was also what made this engineering possible. The fort is part of the self-guided tour. That tunnel, and the system it served, are still intact.
