Originally called the "West Battery", Castle Clinton was built on an artificial island as part of the refortification efforts proceeding the War of 1812 in 1811. Renamed Castle Clinton in 1815, the Fort served a variety of purposes, an entertainment venue (1815-1854), the nation’s first immigrant processing center (1855-1892), and New York City Aquarium (1896-1941). Castle Clinton remains a prominent fixture of the Battery, now serving as a ferry station to Ellis Island.

Named after prominent Continental Army General and Father-in-law to Alexander Hamilton Philip Schuyler, Fort Schuyler is regarded as an exceptionally fine example of the French Fortification style. Built in the wave of construction following the aftermath of the war of 1812, it was dedicated in 1856 and served to protect New York Harbor's entrance to the Long Island Sound. It served multiple uses during its time, including as a prison camp during the Civil War, but it was eventually given to the state and abandoned. Eventually, after a prolonged fight with Robert Moses, the New York State Merchant Marine Academy was able to take it over and still is present in the fort to this day (in addition to a Merchant Marine Museum).

Block House 4 was one of a number of small military forts built before the War of 1812 in order to defend Manhattan from the British. Built on a high outcropping of rock in order to provide a vantage point, the Block House was never used as the British never attacked Manhattan. Eventually, it was torn down to make way a Public School in the 1960s.

Though it was built in the Beaux Art Style to serve as the armory for the New York Army National Guard's First Battalion, 69th Regiment (and still serves as its headquarters), the 69th Regiment Armory is more famous for its impact on the art world. In 1913, the Armory Show was one of the first public displays of Modernist Art, with pieces like Marcel Duchamp's Nude Descending A Staircase provoking admiration and outrage.

The enormous 9th Regiment Armory was built in 1894 and designed by Edward Sargent and W.E. Cable. The armory was hewn out of rough-cut granite and its design featured scrolling, arrow-loops, and towers. Though it housed the 9th Regiment and the 42nd Infantry Division, the 9th Regiment armory also was a host to a series of public gatherings, sporting events, and exhibitions. Its last role before its demolition was that of welfare administration.

The armory that the men of 71st Regiment are seen entering here was actually the first of two built on this spot. This first armory was built in 1892 and was only ten years old when a fire of unknown origins ravaged its interior. The new armory that was built on the ruins of the old was startlingly featuring crenelated towers, an impressive entrance, and an immense tower based on the city hall of Sienna. The building lasted for the better part of a century, but in 1971, in a sorry state of disrepair, it was evacuated and then demolished.

The 23rd Regiment Armory looms over Crown Heights with its castle-like structure and turrets. Built-in 1891-1895 in a Romanesque Revival style, its architects Fowler & Hough as well as Isaac Perry, aimed to evoke a medieval fortification. Initially, home to Brooklyn's 23rd Regiment, the red brick structure stored weapons, contained a vast drill hall, and a series of club-like amenities for its troops and officers. It remained in operation until 1982 at which point it was converted into a homeless shelter.

Designed by William Mundell, the 47th Regiment Armory was built in 1884 on the site of a former baseball grounds. Containing an armory, club rooms, and later a drill hall, the armory was one of the few funded by the state as opposed to Kings County. While the 47th Regiment left the armory in the 1800s, various Army occupants and the National Guard utilized the space until 2011.

Built in 1873, the William Mundell-designed Clermont Armory was, at the time, the largest hall without pillars or obstructions in the United States. Mundell’s ornate Second Empire facade was rebuilt in comparatively bland "Neo-Medieval" style in 1911, the 23rd regiment having relocated to a new and larger armory at Bedford and Atlantic Avenues in 1895. When the National Guard left in 1964, the Clermont Armory became a storage facility for the Department of Sanitation, falling out of use after 1989. The building has since been redeveloped for residential use. It is Brooklyn's oldest standing Armory building.

The Kingsbridge Armory was supposedly the largest armory in the world when it was constructed between 1912 and 1917. It remains the largest armory in New York City. Designed by Pilcher and Tachau, the building occupied nearly 5 acres, and the style of the structure evokes many of the railroad stations built around the time of its construction. Originally the building housed munitions as well as the Eighth Regiment, once known for their role as the honor guard at George Washington's inauguration. The military functions of the massive building ceased in the 1990s.

The Park Avenue Armory s a massive 1880 Gothic Revival structure. The main entrance fronts Park Avenue between 66th and 67th Streets. (This photograph depicts the back end of the building on Lexington Avenue.) Designed by Charles Clinton, the huge structure was the headquarters and administrative building for the 7th New York Militia Regiment. The most well-known feature (certainly in its current use as an art space ) is the 55,000 square foot drill hall. Today the building is still used by a detachment of the New York National Guard, Veterans of the 7th Regiment and the Park Avenue Armory Conservancy, a non-profit that programs unconventional performing and visual arts.

In 1794, with the country in need of a system of coastal defenses, the fledgling government began to fortify the Harbor, including the construction of a fort, later to be named Fort Jay, on high ground in the center of the Island. In 1800, New York transferred the Island to the U.S. government for military use. Between 1806 and 1809, the U.S. Army reconstructed Fort Jay and renamed it Fort Columbus (in 1904, the name would be changed back to Fort Jay). Castle Williams (at right), the second of three historical forts, was built on a rocky outcropping facing the harbor. In 1812, the South Battery, the third fort on the Island, was constructed. During the War of 1812, artillery and infantry troops were concentrated on Governors Island. The recently built fortifications deterred a British invasion, sparing New York the fiery fate that befell Washington, D.C.

The massive fortifications that comprise Fort Wood were built in 1807 to protect New York from foreign invasion. This impressive eleven-pointed fort was renamed Fort Wood in honor of an engineer who died during the Battle of Erie (part of the War of 1812). The Fort had 24 guns and guarded New York's harbor until the 1880s when it became obsolete. Fort Wood would not be simply demolished and consigned to the history books. Frédéric Auguste Bartholdi, the sculptor of the Statue of Liberty, spotted the island and thought Fort Wood would be the perfect base for his monument. The cornerstone of the statue's base was laid in 1884, but the conversion of the Fort into the Statue's pedestal was not finished until April 22, 1886.

The massive brick Classical Revival structure with Romanesque Revival elements served as the headquarters for the 22nd Regimental Armory. Completed in 1911 to the designs of the firm of Richard Walker and Charles Morris. The 22nd Regiment was downsized, merged, and moved around in the mid 20th century. The drill hall became for a time a track-and-field venue for the city's schools (having hosted athletic events even while occupied by the national guard). In the 1980s, the huge building served as a city homeless shelter. In the 1990s Dr. Norbert Sanders (the only New Yorker to ever win the city's marathon) raised $25 million to refurbish the building. Today it houses the National Track & Field Hall of Fame, a large after-school program, and the Millrose Games, the country’s best-known indoor track-and-field event.

Fort Washington was a fortified position that was created (opposite and simultaneously to Fort Lee on the New Jersey Side of the Hudson River) to secure Washington and the Continental Army's retreat from New York.

The neighborhood Fort Green owes its name to General Nathanael Greene who supervised the construction of fortifications there for the Revolutionary War (which were later reoccupied during the War of 1812.) The community surrounding the land started using it as public space shortly after the threat of the War of 1812 passed. By 1847, it was designated Washington Park, and twenty years later, famed landscape architects Frederick Law Olmsted and Calvert Vaux began designing its new layout. In 1897, the new Olmsted and Vaux’s landscape was renamed Fort Greene Park.

Fort Tilden serves as one of the youngest and most recently active military installations on this list. Established in 1917 as Camp Rockaway Beach when the United States entered World War I, it was renamed Fort Tilden in honor of the one time Governor of New York. It quickly became a key part of the modern harbor defense of New York, with modern anti-naval and anti-aircraft batteries being installed throughout the first half of the 20th century, eventually becoming (as pictured) a launch site for the Nike-Ajax missiles. It was decommissioned in the 1970s and turned over to the National Park Service.

The Battery Weed was one of three forts built to protect the Narrows, and throughout the years has had multiple names and additions. First called Fort Richmond upon its opening in 1804, the Fort was then named Fort Wadsworth (it was during this period that the structure pictured was begun.) Finally being renamed Battery Weed in 1965 after the Gettysburg General, the Battery remained in active use until 1994.