This five-sided fort was built between 1839 and 1852 to protect New London Harbor as part of a broad system of coastal fortification undertaken by the federal government. This is the third Fort Trumbull built on this promontory, which was known as Mamacock or Fort Neck.
The granite for the massive walls came from the quarry at Millstone Point. Three walls, with four bastions projecting for the corners, face the water for defense against a naval attack. The ravelin, the angular stone structure to the right of this sign, protected the fort entrance in the event of an attack on land. Cannon mounted in chambers called casemates could fire through openings in the walls, called embrasures. Cannon were also mounted on top of the walls.
During the Civil War, the fort served as a recruiting station. Thereafter, artillery companies served here until 1907, when the army downgraded Fort Trumbull to a supply post. Three new forts had been built on islands at the entrance to Long Island Sound, and these were more important strategically.
This fort is built in the Egyptian Revival style, well suited to its imposing and somber function. The entrance resembles those found on Egyptian temples and tombs. Captain George Cullum of the Army Corps of Engineers directed the construction.