Visible from West Point across the river and traffic on NY 9D passing through Garrison, it has become one of the most recognizable man-made landmarks of the Hudson Highlands.

Castle Rock was bought in 2021 by George Carroll Whipple III, a third generation, Putnam county resident and philanthropist.

[1] In 2010, extensive historic restoration work was completed to repair the entire slate roof, tower, dormers, and chimneys.

To the northeast, on the mountain's summit, is Woodsome Lodge, a rustic log cabin with its own views of the Highlands.

In 1855 Osborn, who had been one of the charter officers of the Illinois Central two years earlier, visited the Highlands to take in the fresh air and scenic beauty of the area.

[1] Osborn also made other improvements to the property, including Woodsome Lodge, and other wings that doubled the size of the original castle.

[1] 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.

[4] In the late 1970s, after the property was listed on the Register, New York's Department of Environmental Conservation bought 129 acres (52 ha) of the former estate,[1] including the meadows along Route 9D, and opened it to the public as the Castle Rock Unique Area.