Go south on Route 604 towards Hackettstown. Turn west (right) onto Route 665 (Bilby Road). Follow this a short distance to Route 517, then go north (right). Check your odometer at this turn and turn right in 1.2 miles onto Deer Park Road. The road starts out as a two lane gravel road and narrows down to one lane, so go slow. If you make a wrong turn and find yourself in someone's driveway, just turn around and take the other fork. Allamuchy Mountain State Park entrance is about a mile up the road.