Fort Carroll Light is a derelict lighthouse on the walls of Fort Carroll in Maryland’s Patapsco River, built because the fort itself created a navigational hazard beside the ship channel. First established in 1854 with a keeper’s house and tower, the light was relocated several times as the unfinished fort was altered, finally reaching a central position on the western wall in 1900, where its fog-bell tower still stands. The army abandoned the increasingly obsolete fort in 1921, and the light had already been automated and discontinued. Neglected afterward, the island never found a lasting new use and instead became a refuge for seabirds.