Originally from Ohio, Edward S. Harkness was to become heir to a fortune initiated by his father's substantial investments in John D. Rockefeller’s Standard Oil. Instilled at an early age with an ardent love for his fellow man and a feeling of responsibility for the wise and just use of the wealth at his command, Mr. Harkness was to bestow over two hundred million dollars upon wide-ranging philanthropies.

The mansion was purchased in 1907 by Edward and Mary Harkness. From 1918 to 1929, extensive work was done to the grounds by noted landscape designer Beatrix Jones Farrand (one of the founders of the American Society of Landscape Architects). The estate was left to the State of Connecticut in 1950 and became part of the State Park system in 1952.

The gates at Harkness Memorial State Park open at 8:00 am and close at sunset, all year. There is no vehicle access to the portion of the park north of Great Neck Road (the Verkades Property); this portion has walk-in access only. There is a daily parking fee for out-of-state registered vehicles at Harkness Memorial State Park