Donated to the Trust in 1974 by the New Jersey Conservation Foundation, the preserve is named for Herbert and Anne Isenburger, previous owners of this property. The parcel is a hillside forest of oaks, sugar maples and ash. At the top of Trimmer Hill, wild turkeys can find acorns and insects as they scratch in the leaves. In early mornings the woods ring with calls from ovenbirds and other forest birds. Chipmunks scurry amongst the same old stone walls where a black snake warms itself on a sunny day. Nestled in a rural, agricultural setting, with nearby pastures and fields, it's common for a red fox to trot along old woods paths as they hunt for food to bring back to hungry kits in their dug-out den.
Visitors use old woods lanes for access for bird watching. Limited roadside parking is available. Hunterdon County Parks' Teetertown Ravine is nearby. No hunting is permitted on this preserve.