The park's lands, heavily mined, logged and quarried in the past, were assembled over the mid-20th century from different purchases by the state, totaling as of 2014. They range from riverside salt marshes to mountain summits, including the highest in the Highlands, the south summit of Beacon Mountain. It is managed by the New York State Office of Parks, Recreation and Historic Preservation (NYSOPRHP) from offices at Fahnestock State Park to the east. Its parcels adjoin others owned by other public agencies and private preserves, some of which are managed by NYSOPRHP as well and are open to the public.