Fort Hamilton is New York City's last active-duty military post. The fort was named for Alexander Hamilton. The first cornerstone was laid in 1825 and the first garrison flag raised in 1831. Fort Hamilton was the first National Guard training facility, opening its doors in 1839.

The earliest recorded use of the location by the military was Narrow's Fort, a small battery that defended New York against the British on July 4th of 1776. Almost 50 years later, a fort was designed on these grounds by French Engineer Simon Bernard in 1825. He had previously served under Napoleon's Army until the emperor's defeat in 1815. The fort was considered a landward defense for Fort Lafayette, an island fortification in the Narrows between Brooklyn and Staten Island that was demolished during the building of the Verrazzano-Narrows in 1959. Fort Hamilton's sister was Fort Wadsworth on Staten Island. During the Civil War, the site included a Prisoner of War Camp and protected New York's Harbor from the Confederate Army. For the duration of World War I and World War II, the fort was used as a mobilization center. In the 1960s it hosted the United States Army Chaplain School, which trained ministers and their assistants for active duty.

Remnants of the original fort on the site include Colonels Row, the Fort Hamilton Community Club, the Lee House, and the Harbor Defense Museum, all of which are on the National Register of Historic Places.