Fort Hamilton's Harbor Defense Museum tells the story of New York City's defenses over time, the Revolutionary War Battle of Brooklyn, and is located in a historic caponier, part of the original fort.
During the first half of the 19th century, the United States was compelled to expand the fortifications protecting its harbors and strategic waterways. Built between 1825 and 1831, Fort Hamilton became part of the Third System of Fortifications built throughout New York City. Today, the Harbor Defense Museum occupies Fort Hamilton's caponier, a freestanding bastion located within the fort’s dry moat. Both structures are on the National Registry of Historic Places.