The house retains most of its original interiors, which were designed in a much more elaborate manner than the facade, though these spaces have been converted to offices.

When Mary died ten years later, she bequeathed the house to the Commonwealth Fund, an organization founded by Edward's mother.

The Edward S. Harkness House is on the northeastern corner of 75th Street and Fifth Avenue, on the Upper East Side of Manhattan in New York City.

[2][9] The Conservatory Water pond at Central Park is directly to the west, across Fifth Avenue,[3] while the Clarence Whitman Mansion is at 7 East 76th Street on the block to the north.

[10] At the time of the Harkness House's construction, it was one of several Renaissance–style mansions in New York City to be built upon a highly visible corner site.

[17] The architectural writer Robert A. M. Stern describes the structure as an early Modern Renaissance–style building in New York City.

[21] The structure is five stories high,[22][23] but the attic (which originally contained servants' quarters) is concealed from street level.

[23] Two leaded windows are installed on the eastern elevation,[26] and an alleyway measuring 12 feet (3.7 m) wide was built to the east of the house as well.

[17][25] The first story is clad with rusticated marble blocks, with deep grooves running horizontally and vertically across the facade.

[21][30] The entrance on 75th Street leads to a plain vestibule with a ceiling vault, which was originally made of glass but was replaced with limestone after the 1920s.

[31][35] West of the entrance hall, on the western end of the first floor, is the reception room, which faces Central Park.

[28][36] The ceiling mural contains representations of various figures such as white women carrying umbrellas, along with monkeys and Chinese men.

[23] The eastern half of the ground floor is occupied by the dining room and butler's pantry,[37] the former of which is raised slightly above the entrance hall.

[28][36] When the building was used as a residence, the dining room had tapestries hung from rods,[36] as well as sconces and chandeliers inspired by old Italian designs.

[23] The music room, on the eastern side of the house, is illuminated by leaded windows[37] and has pilasters on the walls, an ornate cornice, and a coffered ceiling.

[32] As originally designed, the music room had two imported Italian chandeliers,[35] along with tapestries, brocades, and Italian-style wall coverings.

[23] The upper stories were originally used as bedrooms and had carved doorways, sculpted ceilings, and decorative wall panels.

[37] The boudoir, facing Fifth Avenue, has rounded corners and a fireplace and is used by the Commonwealth Fund's vice president and treasurer.

[41] The laundry room was finished with rubber floors and ceramic-tile walls, and it had a gas stove and a washing machine.

[44] After Edward married Mary Stillman Harkness in 1904,[45] the couple lived at 16 East 79th Street four blocks north.

[17][24] In January 1907, Harkness acquired a land lot at the northeast corner of 75th Street and Fifth Avenue, measuring 35 by 115 feet (11 by 35 m), from John R.

[42] In the house's first few decades, it hosted some events, such as a debutante ball for a member of the Stillman family,[57] a dance for the Harknesses' nephew Henry C. Taylor,[58] a meeting for the Dutch consul general in New York City,[59] and a lecture by the pianist Margaret Deneke.

[60] By the late 1910s, Edward Harkness's real estate holdings, including the 75th Street house, were estimated at $1,090,000 (equivalent to $19,156,000 in 2023).

[42] Edward Harkness continued to live at the house until he died there on January 29, 1940;[42][43] his funeral was hosted there shortly afterward.

[75] The Commonwealth Fund formally obtained the house from Mary Harkness's estate in July 1951,[76][77] and the organization renovated the building for use as its headquarters.

[24] In a 1912 article about the mansion, Town and Country magazine similarly described the house as having a modest design in spite of the expensive materials.

[82] A writer for The New York Architect said the house included all the standard features of an upscale urban dwelling, albeit in a way that was "entirely free from exaggeration",[25] a sentiment echoed by the Architectural Record.

[22] According to the Record, the sparing use of ornamentation gave the facade an air of "quiet elegance", as contrasted with the interiors, which were clad with "the best [materials] which it was possible to buy".

[28] A writer for Vogue magazine, in 1915, credited the plain exterior with giving the mansion "the air of reserve with which it should face the world".

[83] The writer John Tauranac cites the architect Donn Barber as saying that the mansion was a "dignified house that would not in an ostentatious way indicate its costliness".