This donut-shaped forest preserve 18 miles southwest of Chicago encircles the Argonne National Laboratory, which lends it a lightly-traveled feel. With the exception of occasional access roads and chain link fences, it feels remote, with almost no hint that you’re looping one of the country’s largest government-funded research facilities.
This route takes a clockwise approach to the preserve’s main loop trail—an 8-foot wide limestone covered beauty—and crosses three roads during the first mile. The trail meanders past the cattail-fringed 91st Street Marsh and cruises dense stands of oak and pine before a short, out-and-back detour to a picturesque waterfall on Sawmill Creek. The main trail skirts the top of the creek’s ravine and heads west through a series of relic foundations before another short detour at mile 5.3. The short climb to the bluff-top overlooking the Des Plaines river valley is worth the huffing and puffing.
Enjoy a sprinkling of ponds, marshes, and more pine plantations before heading north, then east to end the loop. Just before returning to the parking area, a footbridge crosses a lovely section of Sawmill Creek.
Consider coming back on foot to explore other smaller trails, especially on the preserve’s west side.
-Mapped by Ted Villare
- Distance: 16.1
Location: 41.724913, -87.973444
After grabbing a map from the trailhead kiosk on the park's north side, follow the trail near the water fountain and restrooms.
Location: 41.724529, -87.974217
This route follows the trail clockwise around the preserve. Turn left at the first junction after the parking lot. You'll immediately cross Northgate Road and in another 250 yards you'll cross Cass Avenue. Use caution on these street-level crossings.
Location: 41.722798, -87.967608
The trail climbs as it jogs north then south. You'll pass Mile Marker 9 before crossing 91st Street.
Location: 41.721324, -87.960227
A trailside bench sits alongside the wooded banks of the 91st Street Marsh. Stop to watch stands of swaying cattails and swallows twirling over the surface of the water. This marsh, you'll see, is more of a small lake than a marsh.
Location: 41.717918, -87.957995
Trees take center stage on the next stretch of trail where gnarled limbs of stately oaks reach shade the path. Forests of red, jack, and white pine date back to the 1950s when the Argonne National Laboratory planted them for erosion control and as a buffer for the surrounding residential communities.
Location: 41.708372, -87.955592
Near mile 2.6, cross Bluff Road. The trail skirts another trailhead parking area (also with restrooms and water) and you may notice some connector because of high traffic near the Outdoor Education Camp. Continue on the main trail that winds around the parking cul-de-sac.
Location: 41.705961, -87.962476
This route turns right at this road crossing to include a 0.5-mile out-and-back on the Rocky Glen trail. The trail ends at a 5-foot limestone waterfall built by the Civilian Conservation Corps in the 1930s. Though you'll have to drop your bike for the best view, the detour is worthwhile. After backtracking to this spot, follow the path to the west, continuing on the main loop trail.
Location: 41.705264, -87.964042
You'll approach Sawmill Creek again as the trail turns south. The creek flows through an 80-foot-deep ravine on the right side of the trail. Look for black and white oak, as well as bitternut and shagbark hickories, growing on the steep sides of the bluff.
Location: 41.701371, -87.963581
At the T-junction, jog left then right to stay on the wide, limestone-covered trail. You'll dip toward the trail's lowest point and cross the creek near some train tracks up ahead.
Location: 41.696533, -87.97225
After the electrical switching station, you'll pass through an area that served as a plant nursery for Chicago parks. Look for several concrete-and-stone building foundations from the early 1910s, when the nursery was in operation.
Location: 41.69312, -87.983057
Stay straight on the service road where the trail makes a sharp right. You'll make a short climb to an overlook offering an expansive view of the Des Plaines River valley and the small town of Lemont to the south. After enjoying the view from the trailside bench, backtrack about 150 feet and turn north on the trail.
Location: 41.696837, -87.994387
You may notice a buzzing sound on the loop's southwest corner. It might be coming from the model airplane field, which sits on the edge of a large prairie, or it might be from the laboratory itself which is a center for government energy studies.
Location: 41.701091, -88.001422
There are many smaller and even some unmarked trails criss-crossing the preserve. This northbound trail, the Kettle Hole Trail, re-connects with the main loop trail in 0.8 miles, but isn't open to bicycles. After the pond, stay on the wide, paved path that turns north about 300 yards from here.
Location: 41.702653, -88.004555
At mile 6.9, you'll pass another restroom-equipped trailhead access point. Stay straight on the main loop trail to continue toward the end of the loop.
Location: 41.712388, -88.00279
Turn right at Westgate Road to parallel it for about 500 feet before crossing to the trail on its north side. You'll turn left at the junction with the Tear-Thumb Trail, bypassing it in favor of the more forested main loop.
Location: 41.721017, -87.984134
After scouting for great blue herons near the Tear-Thumb Marsh, a small footbridge leads over Sawmill Creek. The loop-end parking lot is straight ahead.
Location: 41.720926, -87.959883
More of a lake than a marsh, there's a bench on the wooded banks of this pond on the loop's northeast corner.
Location: 41.717538, -87.957573
A local resident of this 2,689-acre preserve.
Location: 41.712149, -87.953017
Shading the trail, these stately Oak are a highlight of the loop's east side.
Location: 41.705729, -87.965033
Oddly, this picturesque waterfall didn't inspire the name for the forest preserve. It is actually named for a man named Seymour Waterfall, a former director of the county forest preserve system.
Location: 41.705119, -87.964175
You'll catch glimpses of Sawmill Creek through the trees.
Location: 41.696533, -87.972636
Ghosts of the forest preserve's past: these old buildings were once part of a botanical garden.
Location: 41.700766, -88.001002
This pond precedes the turn off for the Kettle Hole Trail. Skirt it on your right and continue following the wide, gravel trail alongside the railroad tracks.
Location: 41.718711, -87.994435
The rolling 8-foot wide trail is open to cyclists, horseback riders, and hikers. It's surface is covered in small limestone gravel.