This hike is considered to be one of the most challenging routes in NJ. It has a little bit of everything from road walking to steep climbs without switchbacks. After the road walk, the hike starts on what appears to be a woods rd and the first turn-off to the left is not marked so you have to watch for it on the phone/GPS. A lot of the climbs have a 20% grade. After you complete this hike, you will understand why it is “accessible from March until October.” Some areas of the trail are so rugged that when covered with snow/ice they would be impassable. The hike might be easier in the counterclockwise direction where you go up most of the rock scrambles rather than down them.
We started the hike at the Stonetown Recreation Center Parking Lot and went clockwise following the route recorded by John Watson. Our mileage and elevation gain were slightly different due to losing the trail, bushwacking to views, etc. Stats from my Garmin GPS were 11.0 miles and 3174 ft elevation gain. We completed the hike in 6 hrs with an avg pace of 1.8 mph.
We did the 'extended' loop from the ball field going counter clockwise. The extended loop follows the highlands trail crossing the road at the dam then coming up the backside of Harrison Mountain on the red blaze trail. The hike was great and we had great weather (mostly cloudy ~80 degrees). It took ~6.5-7 hrs to complete with a few quick breaks mixed in. As others have said, this is a vigorous hike so go prepared and plan on being sore for a few days after. The Highlands Trail portion was very rewarding with a number of nice look out points. The backside of the loop didn't have as many views and was marred by numerous ATV trails, but there are a few quiet glades to keep you motivated. Lots of wild life sightings as well: toads, deer, raptors, and discarded opossum and deer bones. I also had my own personal swarm of mosquitoes to keep me company for awhile. The trail is easy to lose if you are distracted so make sure you keep an eye on the blazes; we had to back track 50 feet or so a few times to find the 'right' trail. Also, we did hear a lot of semi-automatic small arms fire while going through the Norvin Green State Forest section. Just as we started to get nervously close and signal that we were in the area, the trail turned and headed in the opposite direction. Just something to keep in mind when going through multi-use areas. Overall, a great hike and would definitely do it again. It could be a good training hike when preparing for a bigger trip.