The reservation sits on a ridge of volcanic basalt formed roughly 200 million years ago.
The park was created in the 1920s when the Passaic County Park Commission acquired the Lambert estate.
Lambert Castle was designed by architect George Post, who also designed the New York Stock Exchange building.
The mountain is a documented stopover for migratory raptors, including red-tailed hawks and ospreys.
The structure of the castle was modeled after English baronial architecture rather than traditional American styles of the era.
During the Great Depression, the castle served as a museum and office space for the Passaic County Park Commission.
The park's altitude reaches approximately 500 feet above sea level at its highest point.
Garrett Mountain Reservation is a 568-acre park located on the First Watchung Mountain in Passaic County, New Jersey. The focal point of the property is Lambert Castle, a historic stone residence built in 1892 by silk magnate Catholina Lambert. The reservation features miles of paved and unpaved trails that navigate through wooded sections and open fields. Visitors have access to designated equestrian trails and cross-country running paths. The site offers elevated vantage points providing views of the New York City skyline and the surrounding suburban landscape. The grounds include the Barbour Pond, which is periodically stocked with fish for recreational angling. Recreational facilities include basketball courts, softball fields, and multiple picnic groves equipped with tables. The park serves as a migration corridor for various bird species, drawing birdwatchers during spring and fall seasons. The terrain is characterized by basalt cliffs and rocky outcrops typical of the Watchung Mountains geology.
The stone terrace directly in front of Lambert Castle, which provides the clearest panoramic view of the skyline.
Wear sturdy hiking shoes, as the trails contain loose rocks and uneven volcanic terrain.
Bring binoculars if you are visiting during spring or fall migration periods for optimal wildlife viewing.
Check local event calendars before visiting, as the park frequently hosts regional cross-country meets and community festivals.
Do not attempt to access areas marked for rehabilitation or habitat restoration, as the trails can be slippery and hazardous.
Leash laws are strictly enforced for pets; maintain distance from wildlife; pack out all trash.
