| Edward S. Harkness House | |
|---|---|
 The main elevation of the facade on 75th Street | |
 | |
| General information | |
| Type | Mansion |
| Architectural style | Modern Renaissance |
| Address | 1 East 75th Street |
| Town or city | New York, NY 10021 |
| Country | United States |
| Coordinates | 40°46′28″N 73°57′55″W / 40.77444°N 73.96528°W |
| Current tenants | Commonwealth Fund |
| Construction started | 1907 |
| Completed | 1909 |
| Cost | $550,000 |
| Client | Edward Harkness |
| Owner | Commonwealth Fund |
| Technical details | |
| Floor count | 5 |
| Design and construction | |
| Architect(s) | James Gamble Rogers |
| Designated | January 24, 1967[1] |
| Reference no. | 0415[1] |
The Edward S. Harkness House (also 1 East 75th Street and the Harkness Mansion) is a Modern Renaissance–style mansion at the northeastern corner of Fifth Avenue and 75th Street on the Upper East Side of Manhattan in New York City, United States. Built between 1907 and 1909, it was designed by James Gamble Rogers for the philanthropist and oil heir Edward Harkness and his wife Mary Harkness. The mansion, which has been the Commonwealth Fund's headquarters since 1952, is a New York City designated landmark.
The Harkness House is five stories tall and has a facade made of Tennessee marble, with few exterior decorations. Because the mansion has a longer frontage along 75th Street than on Fifth Avenue, the main entrance is through a portico on 75th Street. The rest of the facade has windows with carved sills and lintels. 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. The ground floor contained a reception room and dining room, and the second floor had a salon, music room, and library. There were also servants' rooms in the basement and attic, as well as bedrooms for the Harkness family on the third and fourth floors.
Edward Harkness acquired the site at the northeast corner of 75th Street and Fifth Avenue in January 1907. When the house was completed, it was one of seven residences that the Harkness family owned. Edward lived there until his death in 1940. When Mary died ten years later, she bequeathed the house to the Commonwealth Fund, an organization founded by Edward's mother. After the Commonwealth Fund converted the house into offices, the organization used the building as its headquarters. By the late 20th century, the Harkness House was one of a relatively small number of pre–World War I mansions remaining in the area. Commentary of the house's design has been largely positive, focusing on the simplicity of the facade.