Designed in the Gothic Revival style by Charles Clinton for the 7th New York Militia Regiment, the Park Avenue Armory was completed in 1880, with two expansions in the early 20th century.

The 53rd Digital Liaison Detachment of the New York Army National Guard, the Veterans of the 7th Regiment, the Knickerbocker Greys cadet corps, and the Lenox Hill Neighborhood House also occupy parts of the armory.

Numerous spaces in the interior of the building were designed in several styles by decorators such as Louis Comfort Tiffany, Stanford White, Kimbel and Cabus, Alexander Roux, Francis Davis Millet, and the Herter Brothers.

In 2000, the state awarded the Park Avenue Armory Conservancy the responsibility of overhauling the building, restoring the dilapidated interior spaces, and transforming it into an arts venue.

The six-block site was intended to be developed into a public park called Hamilton Square, but the plots were instead leased to educational, medical, and charitable institutions.

[17][16] The arched doorway at the center of the Lexington Avenue facade was originally fitted with a heavy iron gate and thick oaken doors.

[35] On the first floor of the administration building, the regimental rooms are divided into northwest, southwest, and eastern sections by a west–east entrance hall and a north–south main corridor.

[42][47][48] Other people involved in the design included Samuel Colman, who did the stenciling; Candace Wheeler, who created the embroideries; and possibly Lockwood de Forest, who may have provided some of the woodwork carving.

[50] On the north wall is a mosaic-tile fireplace; a wooden mantel measuring almost 10 feet (3.0 m) tall, which depicts an eagle attacking a sea dragon;[44][49] and a plaster overmantel with stained-glass windows on either side.

[111] The Company M room contains oak woodwork, a fireplace, paneled ceiling, a door to the drill hall's mezzanine, and stairs and a gallery on the east wall.

[115] The room for Company D has elaborately carved mahogany woodwork (including lockers), lamps, a chandelier, and a mantelpiece;[116] it also had ornate stenciling on the walls, frieze, and ceiling.

[110][118] In the quarters of Company G, there are carved woodwork, lockers, a mantel, and original polished-steel lamps, although the ceiling paneling and wall stencils were painted over in 1894.

[137] Clark said the Tompkins Market Armory's drill room could fit only two companies at once, and the third floor of the structure was not strong enough to support military exercises.

[xii][236] The Charles Meads Company was hired for the renovation,[94][236] which was completed in early 1913;[97][98] the project involved new seating areas and modifications to accommodate tennis games.

[250] The same year, the New York Court of Appeals ruled that the city's Board of Estimate had to pay $8,000 annually toward the armory's upkeep,[251][252] and the 107th Infantry became the 207th Coastal Artillery.

[259][260] Although the city and state governments unofficially did not oppose the plan (since they would be able to profit from the new structure),[260] the development would have required renegotiating the regiment's lease of the site.

[268][269] Despite this, the state government began studying plans in January 1981 to erect a tower over the armory,[24][270] generating opposition from figures such as former U.S. first lady Jacqueline Kennedy Onassis[271] and U.S. Representative Mario Biaggi.

[301] Initial plans entailed converting the drill hall to a multi-use space with a 4,150-person capacity, which was later limited to 1,500 because of worries that traffic in the area would worsen.

[307] In an attempt to prevent the Empire State Development Corporation from taking over the armory, 7th Regiment veterans sued mayor Michael Bloomberg and governor George Pataki in early 2005.

[323] The Swiss architectural firm Herzog & de Meuron was hired to restore the interior of the Park Avenue Armory,[324][325] completing a renovation of the Officers Room in late 2013.

[352] Other events at the armory in its first decade included elaborate galas,[353] lawn tennis games,[354] vocalists' concerts,[355] and the annual musters and inspections of the 7th Regiment's troops.

[370] The armory's events, which included fairs, balls, games, concerts, and drills,[266][323] were attended by figures such as the Prince of Wales Edward VIII in the 1920s[371] and the Queen Mother Elizabeth in 1954.

[387] The 1937 live broadcast of the radio play The Fall of the City by Archibald MacLeish took place at the armory,[388] and the building's first-ever Mass occurred in 1941.

[399] The building has hosted large events and exhibitions such as the 1916 convention of the General Federation of Women's Clubs,[400] the Girl Scouts' annual spring reviews,[401] and the New York Poultry Show.

[418] At the beginning of the 21st century, the building hosted events such as a rally for 9/11 survivors,[419] military award ceremonies,[420] a memorial service for Merce Cunningham,[421] and an exhibit on its own history.

[431] As the building's resident nonprofit arts organization, the Park Avenue Armory Conservancy has hosted and created music, dance, theater, and multidisciplinary artistic works in the drill hall and other spaces.

[345] In the 2010s, those included works by Douglas Gordon,[432] Nick Cave,[433] Martin Creed,[344] William Kentridge,[434] and Hito Steyerl,[435] as well as New York City's first powwow in over 200 years.

[446] When the armory was completed, the Veterans Room was characterized as having tiles that gleamed "as if a bit of the Atlantic furthest from shore had been caught and pressed into service".

[447][448] The King's Handbook of New York described the rooms in 1892 as being "beautifully decorated and elegantly furnished",[25] while an 1895 source called the armory "a handsome building well adapted for its purposes".

[41] Robert A. M. Stern and the co-authors of his 1999 book New York 1880 wrote that the armory "set a standard of quality in the care taken with the building itself and especially in the lavish appointments on the interior that was never achieved elsewhere".