Prequel: Sandy Hook, Key to The City
To enter New York Harbor, ships need a deep channel. Until the 1900s, that meant sailing next to the shore of Sandy Hook. This gave the small peninsula a big role in the safety and defense of New York Harbor for more than a century before Fort Hancock was built.
In 1764, the Colony of New York built Sandy Hook Light to assist navigation. Because the lighthouse helped ships sail safely to New York Harbor, the structure has always had inherent military value. As a result, a military presence quickly followed its construction and has remained more or less since the American Revolution.
In early 1776, Sandy Hook peninsula was easily captured by the British. In June 1776, Continental Army Lt. Col. Benjamin Tupper led his artillery to destroy the lighthouse, "but found the walls so firm I could make no Impression." Unlike most of New Jersey, both the Sandy Hook Lighthouse and New York City remained in British and Loyalist hands until the war's end in 1783. Loyalists guarded the Light for the remainder of the War, using the Hook to stage raids on patriot-held areas in New Jersey. The cannonball-dented remained visible until repairs took place just before the Civil War, when the walls were thickened considerably.
During the War of 1812, a wooden fortification named Fort Gates was constructed in 1813, an example of what is now called the Second System of defense. The lighthouse itself was armed with cannon. The Federal Government completed purchase of the peninsula in 1814.
After the War of 1812, recommendations were made to construct a large permanent fortification at the end of the Hook, but it wasn't until 1857 that work began. Over the next three years, a large wharf was constructed to receive new building supplies and materials and the fortification of the fort was laid out. In 1859, the U.S. Army began to construct the Fort at Sandy Hook. It also served as a camp for the 10th New York Volunteer Infantry, or the "National Zoauves." The fort was never completed, however, and was deserted after the war. (The granite structure was largely torn down by the Army in the 1950s.) This represented the Third System of defenses.
Starting in 1890, the Army constructed the first of many concrete gun batteries of the Endicott era. Next were Taft Defenses that included changes to existing fortifications and the addition of 12-inch barbette guns. (The Army also created the Sandy Hook Proving Ground in 1874, which remained a separate entity until it was moved to Maryland in 1919.)