Known also as the John D. Rockefeller Estate, Kykuit is a 40-room historic house museum in Pocantico Hills. The house was built for Rockefeller family patriarch John D. Rockefeller. Conceived largely by his son, John D. Rockefeller, Jr., and enriched by the art collection of the third-generation scion Nelson Rockefeller, it was home to four generations of the family. The house is a National Historic Landmark owned by the National Trust for Historic Preservation, and tours are given by Historic Hudson Valley.
(from the Kykuit wiki.)
Hudsonvalley.org has a wonderful site on Kykuit with tour information, hours, and further reading on the Rockefeller family.
Want to learn more? Head here.