Sourland Mountain Preserve Loop


This hike loops around this Somerset County park, passing through several interesting boulder fields.

4 hours
Easy to Moderate
5.6 miles
Route Type:
Allowed on leash
First Published:

Daniel Chazin



View Sourland Mountain Preserve in a larger map

Trailhead GPS Coordinates
Driving Directions

Take I-80 west to Exit 43 and proceed south on I-287. Take Exit 17 and continue south on US 206 for about 7.2 miles. Turn right onto Amwell Road (County 514) (do not turn right at New Amwell Road) and proceed for 2.8 miles to East Mountain Road. Turn left onto East Mountain Road and follow it for 1.9 miles to the entrance to Sourland Mountain Preserve, on the right. GPS address: 421 East Mountain Road, Hillsborough, NJ 08844.


White Square Trail as it passes by a group of boulders -- Photo by Daniel ChazinSourland Mountain is a ridge which straddles the borders of Somerset, Hunterdon and Mercer Counties. Due to the harshness of the land and its unsuitability for farming, large portions of the ridge have remained undeveloped. The largest protected portion of the ridge is in Somerset County, where about 4,000 acres have been set aside as a preserve, administered by the Somerset County Park Commission. 

The preserve offers three loop trails, marked with white blazes with the logo of the Somerset County Park Commission. The white-triangle-blazed Maple Flats Trail and the white-circle-blazed Pondside Trail are short, easy loop hikes. The five-mile-long white-square-blazed Ridge Trail, which passes through an interesting boulder field, is more challenging, and it permits one to spend several hours exploring this beautiful preserve. A trail blazed with red circles traverses another boulder field. Finally, there are several short connecting trails, marked with “C” blazes on a white background. This hike follows the Ridge Trail and the Red Circle Trail (none of the short connecting trails are included in the route of this hike). 

Near a small kiosk at the edge of the woods, you will notice a wooden post with three blazes – white triangle, white circle and white square. This marks the start of the three loop trails, which head uphill into the woods, passing a number of fallen trees, and paralleling a brook on the left. Note the many beech trees, with exposed route systems, along the trail.

In about five minutes, you’ll reach post #1 (all intersections are marked with white-on-green reflective numbers on wooden posts). Here the white-triangle and white-circle trails turn left, crossing the stream on a footbridge, but you should continue ahead on the white-square-blazed Ridge Trail.

The white-square-blazed trail proceeds steadily uphill (you’ll climb a total of about 400 vertical feet during the first part of the hike), skirting a small boulder field. It goes through a heavily wooded area, far removed from the homes and farms that you passed on your way to the park. In about ten minutes, the trail levels off and a connector trail (with “C” blazes) begins on the left. Continue ahead on the white-square-blazed trail, which soon resumes its climb. 

Balanced rock ontop of a larger boulder along the Red Circle Trail -- Photo by Daniel ChazinAfter leveling off again, the white-square-blazed trail climbs a little more and reaches an area of huge boulders. The first gigantic boulder is just to the left of the trail, but you’ll encounter many other large boulders in the next half hour or so. This is the most interesting part of the hike, so take your time to enjoy the unusual boulders. You’ll pass several overhanging boulders, as well as rocks perched atop large boulders. At one point, the trail goes through a narrow passage between two huge boulders. (Take care to follow the white square markers, as there are a number of unmarked trails in this area.) Towards the end of the boulder field, be alert for another unique feature of this trail – a large tree that has grown out of a horizontal crack in a boulder! 

The trail continues through a forest that features many tulip trees – tall, straight trees, with no branches below the treetops. You’ll notice a number of multiple tulip tree trunks growing out of the same roots.

Finally, after about an hour of hiking, you’ll reach post #4. To the left, a connecting trail leads back towards the parking area, but you should bear right to continue along the white-square-blazed trail. In another 200 feet, you’ll come to another junction. Here, the white-square-blazed trail bears left, but you should turn right onto the Red Circle Trail, which crosses a stream and proceeds through another boulder field, climbing gently.

In about 15 minutes, you’ll pass through a gap in a chain-link fence. Just beyond, the trail crosses a gas pipeline. Soon, the trail winds through another boulder field, passing a number of interesting large boulders. For much of the way, the trail route is relatively level, but it eventually descends a little.

After following the Red Circle Trail for about 45 minutes, you’ll reach a junction where a connecting trail begins on the left. Bear right to continue on the Red Circle Trail, which soon begins a steady descent towards Roaring Brook, passing a large overhanging rock on the left.

In a short distance, you’ll come to a T-intersection. Here, the Red Circle Trail ends, and you should turn right onto the white-square-blazed Ridge Trail. The trail continues to descend parallel to Roaring Brook, below on the right. Soon, you’ll reach post #7, marked by a huge cairn. Another connecting trail begins on the left, but proceed ahead on the white-square-blazed trail, which descends on switchbacks and continues parallel to Roaring Brook.

Just beyond an open gate in a chain-link fence, you’ll reach post #8. A connecting trail goes off to the left, but you should proceed ahead on the white-square-blazed Ridge Trail. Just ahead, the trail approaches Roaring Brook (note the cascades in the brook), then bears left and heads away from the brook.

Hiker crossing a boardwalk on the White Square Trail -- Photo by Daniel ChazinIn another 15 minutes, you’ll cross a boardwalk over a stream and pass an old stone-and-concrete wall (possibly built as a dam) to the left of the trail. Just beyond, you’ll come to a four-way intersection marked by post #9, where you should continue straight ahead.

The next stretch of trail is nearly level, and it features a long boardwalk and many short stretches of boardwalk. In another 20 minutes or so, you’ll reach post #10. Here, you’ll encounter the white-triangle-blazed Maple Flats Trail once more. Turn right and follow both white-square and white-triangle blazes.

Soon after traversing another long stretch of boardwalk, you’ll again cross the gas pipeline (marked by post #11). Continue straight ahead, soon reaching post #12, where the white-circle-blazed Pondside Trail joins from the left. Here, you should turn right, now following all three trails – white triangle, white circle and white square. Just ahead, you’ll emerge onto a grassy area and descend towards a small pond. Bear left around the pond, pass post #13, and you’ll reach the parking area where the hike began.

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Sourland Preserve Loop Hike

I did the loop on Memorial Day (hot humid) - an interesting trail but not among my top-ten in the state. The Devil's Half Acre is cool and worth the trek. Pictures from my hike at Sourland Preserve - For me, I did not find Rolling Rocks all that exciting -but perhaps after a major rain storm or winter thaw.... and as noted before - From #6 you can take the Red Square to the Rocks -then continue up to #8.


It is now permissible to cross through the fencing to see the huge boulders around Roaring Brook. This arrangement was made with 3M Company some time ago. My source for this is Sgt. Phil Richards of the Somerset County Park Rangers. I call Phil from the trail all the time about downed trees, whatever. This park is close to home for me, so I hike it frequently. I highly recommend hiking the big trail, the Ridge Trail, with the square blazes, backwards, clockwise, 13 to 1. That way, the long walk in from 13-9 is a good warm up. If you hike 1-13, from 9-13 is just a long, often wet, slog out. With the boulders, boulder field at the brook. and incredibly thick foliage, Sourland comes close to rivaling some Highlands area hikes. Don't miss it.