In March 1964, it was designated a National Natural Landmark for its old growth climax hemlock forest and the gorge of the Mianus River.

[4] In 2007, The Nature Conservancy purchased eight acres (32,000 m2) of adjacent wetlands to protect the gorge and its watershed.

The old Hobby Hill pegmatite quarry is located in the northern section of the preserve.

They did so to decrease the risk of excessive deer populations causing damage to the vegetation.

[8] There are numerous species of trees, shrubs, vines, herbs, and ferns within the preserve.