Greentree

Greentree is a 400 acre estate in Manhasset, New York on Long Island. Payne Whitney purchased the estate for his bride, Helen Hay, in 1904. Later, John Hay Whitney and his second wife, Betsey, occupied the main house, where Mrs. Whitney remained in residence there until her death in 1998.

The estate features a real tennis court in good condition, but it is no longer in use.

The estate hosted the Manhasset negotiations, a round of talks between Morocco and the Polisario Front, August 10-12 2007, as part of a set of UN-led meetings. The talks centered on the future of Western Sahara, specifically Morocco's push for autonomy, but not self-determination over the area.