Located in Brooklyn, the site of what is now Fort Hamilton was originally used as a firing ground against the British fleet, on July 4, 1776, as they entered the Verrazano Narrows. Only one ship, HMS Asia, was damaged and the British were able to land. The incident left Americans with the knowledge that military installations on the east coast were an integral part of the nation's defense. The War of 1812 drove home the need for solid coastal defense, after the British bottled the major American ports, and had little difficulty landing troops; the New York harbor was blockaded, but had an effective coastal defense, preventing the British from attacking New York.


The coastal defense fortresses of the War of 1812 were effective, but primitive earthworks built on soft ground, and in 1825 what is today Fort Hamilton was laid out, garrisoned, and built with granite. It was originally called Fort Lewis, but generally called Fort Hamilton (after Alexander Hamilton, one of the Founding Fathers, and the nation's first Secretary of the Treasury) from its very early days; the official name change to Fort Hamilton did not come until the 20th Century.


The fort was part of a system of coastal batteries, arranged with overlapping fields of fire with Fort Lafayette (destroyed to make way for the Verrazano Narrows Bridge), Fort Tompkins, and Fort Richmond to guard the Narrows. Forts Tompkins and Richmond later merged to create Fort Wadsworth, which itself is no longer a military post.


In 1839 the Federal government gave the 27th Regiment permission to hold drills at the fort, making it the United States' first National Guard Training camp.The mission of Fort Hamilton to this day includes being a source of Military Installation support for the United States Army Reserve and the Army National Guard. Other units established at Fort Hamilton were the 12th Infantry Regiment in 1861, the 21st Infantry Regiment in 1862, and the 5th Coast Artillery in 1925.


In the 1880s Secretary of War William C. Endicott recognized that the US's coastal defenses had aged and were no longer up to their mission. A new round of fortification followed, and the guns were upgraded from muzzle loading smoothbore guns to breech loading rifled disappearing guns, and electrically controlled barrier mines. This defense system and weapons were successful; not only were they never used, they were never challenged.


Fort Hamilton has seen the Civil War and two World Wars. During the Civil War, the post protected the harbor against Confederate Raiders, and provided troops to control the Draft Riots, and in both World Wars the fort served a critical role as an embarkation and separation center. The last shore defense gun was removed in 1948, no enemy having ever sailed under its range. In the 1970s the post was the home of the United States Army Chaplain and Chaplain Assistant school, until the school was moved to Fort Jackson, South Carolina.


Presently, Fort Hamilton is the only military installation in the New York Metropolitan area, and is the home of the New York City Recruiting Battalion, the Military Entrance Processing Station, the North Atlantic Division Headquarters of the United States Army Corps of Engineers, the 1179th Transportation Brigade and the 722nd Aeromedical Staging Squadron.