Fort Carroll is a 3.4 acre artificial island and abandoned fort located within the shadow of the Francis Scott Key Bridge. The fort was designed by then Brevet-Colonel Robert E. Lee, and construction was started in 1848 by the U.S. Army Corps of Engineers under Lee’s supervision. The fort was named for Charles Carroll of Carrollton, the last living signer of the Declaration of Independence. Before it was created, the only military defensive structure between Baltimore and the Chesapeake Bay was Fort McHenry. Additionally, a lighthouse (now abandoned) was built to aid navigation into Baltimore’s harbor.
Though never completed and never used as a fort, the architecture is quite amazing, featuring curved granite stairs, brick archways, etc. It originally had 350 cannon ports, a blacksmith shop, carpentry shop, and a caretaker's House. In 1864, it was flooded by torrential rains and declared vulnerable and obsolete. Subsequent uses of the fort included storing mines during the Spanish-American War, holding seamen, and as a pistol range. Most of the steel was salvaged for the war effort and the government abandoned the fort in 1920.
While there have been plans over the past ninety years to redevelop the site, nothing was able to come to fruition and it has fallen into extreme disrepair.