Harbor Hill was a spectacular Long Island mansion built from 1899-1902 in Roslyn, New York, commissioned by Clarence Hungerford Mackay. It was designed by McKim, Mead, and White, with Stanford White supervising the project. It was the largest home he ever designed.[1]

Clarence Mackay (1874–1938) was the son of Comstock Lode magnate John William Mackay, and inherited much of an estimated $500 million fortune upon his father's death in 1902 (approximately $13 billion in 2012 dollars). White collaborated closely with Clarence Mackay's wife, Katharine Duer Mackay (1880–1930), and with her approval, based the main façade of Harbor Hill upon that of François Mansart's Château de Maisons of 1642, using a mix of other influences to finish the overall design.