New Jersey

Johnsonburg Swamp Nature Preserve

Location: Frelinghuysen township, Warren County and Green township, Sussex County

Acres protected: 714 acres

Established: 1990

Managed by: The Nature Conservancy

Why is This Land Special?
Johnsonburg Swamp Preserve protects a limestone forest and is considered one of the most important and species-rich natural areas in the state. Mud Pond, at the heart of the preserve, is a limestone wetland providing excellent habitat for rare plant species, along with waterfowl and other wildlife. The scenic limestone outcrops that overlook the pond to the west and north are the largest rock formations of their kind in the state. It is this limestone bedrock that produces the calcium-rich soil in which Johnsonburg's rare plants flourish. Examples include hoary willow (Salix candida), ebony sedge (Carex eburnea), leathery grape-fern (Botrychium multifidum), white-grained mountain rice grass (Oryzopsis asperifolia) and lesser bladderwort (Utricularia minor), which is found at only three other sites in New Jersey. This carnivorous plant produces yellow flowers and floats in the water, where it periodically extends the equivalent of a small trap door that sucks in insects that brush against it. Threatened wildlife that make their homes around Mud Pond include great blue herons (Ardea herodias), red-headed woodpeckers (Melanerpes erythocephalus), barred owls (Strix varia), red-shouldered hawks (Buteo lineatus), wood turtles (Clemmys insculpta) and longtail salamanders (Eurycea longicauda longicauda). Red-spotted newts (Notophthalmus viridescens), though not threatened, are commonly found in the moist forested areas of the preserve.

Samuel Green, a prominent surveyor, was the first European settler in the area in 1730. For the next two centuries, agriculture dominated the landscape. In recent decades, dairy farms dotted the rolling hills of the area, and the Erie-Lackawanna Railroad roared through Johnsonburg. In the 1970s the railroad closed. Today, the area is beginning to see an increase in housing development.


Visitation Guidelines

  • Please stay on the trail.
  • No fishing, hunting, trapping or collecting.
  • Motorized vehicles and aircraft are prohibited.
  • Bicycling, camping, fires (other than authorized prescribed fires), firearms, rock climbing, spelunking, swimming and feeding animals are prohibited.
  • Horseback riding is by permit only.
  • Pets (except for seeing-eye dogs) are prohibited.

A trail exists for hiking and sight-seeing.

The preserve is open from dawn until dusk.

View a Trial Map.


Take Route 80 West to Exit 19/Hackettstown-Andover. Stay in right lane until the end of exit ramp. At the end of ramp, cross over Route 517 to Route 667 North. After 1/4 mile, turn left onto Route 612 and continue approximately 5 miles to its intersection with Route 519 (stop sign). At intersection, turn right. Route 519 continues straight into Route 661. Proceed on Route 661 until it meets Route 94 (stop sign). Run right onto Route 94 North. The Frelinghuysen School will be on the left approximately 0.2 mile on Route 94.

*Trail begins across Route 94 from parking lot-follow edge of fields then proceed left.


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