Harbor Hill

Clarence H. Mackay (1874 to 1938) inherited part of the Comstock silver fortune and became a major figure in the international telegraph business. With his wife, Katherine Duer Mackay, he commissioned Stanford White of McKim, Mead and White to design a country house on the highest ground overlooking the village of Roslyn and Hempstead Harbor. White designed the house in 1899, and it was built from 1900 to 1902. The Roslyn Landmark Society describes both the main house and its gate lodge as French Baroque, with stone walls and steep roofs.

Local accounts of the estate's size range from 512 to 648 acres. Formal gardens and terraces surrounded the house, and a 70-acre farm supplied it. In 1920 Mackay installed at the foot of the west garden two 26-foot replicas of the Marly Horses, carved by the sculptor Franz Plumelet. The Mackays entertained on a large scale. The National Trust for Historic Preservation reports that F. Scott and Zelda Fitzgerald attended a party there in 1923 and that the next year the Mackays gave their largest party, in honor of the Prince of Wales, with two orchestras and an American flag of light bulbs on the roof.

After Mackay's death in 1938 the estate passed to his son, John Mackay III. According to the National Trust, the grounds were leased to the Army Air Corps, and the empty house fell into disrepair and was vandalized during the Second World War. A demolition crew took the house down in 1947. Developers bought the gate lodge property in 1954, and in the late 1950s the estate land became the Country Estates housing development. Roslyn High School also stands on part of the former estate.

Three buildings survive and were listed on the National Register of Historic Places in 1991. The Gate Lodge, at the junction of Harbor Hill Road and Roslyn Road, was designed as a miniature version of the main house to announce the estate from the public road. It served as a swim club building from about 1970 to 2008, passed to the Village of East Hills in December 2021, and is being restored by the village with the Roslyn Landmark Society. The Water Tower, also by McKim, Mead and White, stands on Redwood Drive between Lincoln Drive and Lufberry Drive. The Dairyman's Cottage at 40 Elm Drive is credited by the National Park Service to Warren and Wetmore. The John Mackay III house and stretches of the old entrance-drive walls also remain.

The two Marly Horse statues were restored and moved. The south statue now stands in Gerry Pond Park in Roslyn, and the north statue, the Horse Tamer, is in the parking lot of Roslyn High School. None of the surviving buildings is open, but the Gate Lodge and Water Tower can be seen from public streets in East Hills.