Osborn also made other improvements to the property, including Woodsome Lodge, and other wings that doubled the size of the original castle. Most of these were architecturally sympathetic to Slade's original design, and there has been little change to it since then. In 1974, William Henry Osborn II, one of Henry Fairfield's younger sons, donated the southern portion of the property, which includes Sugarloaf Hill, to the State Parks Council for eventual inclusion in Hudson Highlands State Park. In the late 1970s, after the property was listed on the Register, New York's Department of Environmental Conservation bought of the former estate, including the meadows along Route 9D, and opened it to the public as the Castle Rock Unique Area. Hiking trails now lead through it and up the mountain; however the house property remains private.