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Green Monster 25K

  4.0 ( 1 ) Favorite


15.6 mile 25.1 kilometer loop
84% Runnable


Ascent: 3,415' 1,041 m
Descent: -3,411' -1,040 m
High: 2,300' 701 m
Low: 1,267' 386 m


Avg Grade: 8% (5°)
Max Grade: 67% (34°)


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Trail shared by Tyler Upham

A 25k race course that has some STEEP inclines and declines.

Tyler Upham

Features Fall Colors · River/Creek · Views · Waterfall · Wildflowers · Wildlife

Limited parking at the trailhead, but plenty of parking a little down the road at the USGS fish lab.


A challenging course in the mountains of the Tioga State Forest.


The Green Monster Trail Challenge is 16.6 mile race through the Mountains in the Tioga State Forest of Asaph, PA.

The race begins with 1.0 mile warm-up on Straight Run Road before reaching the Green Monster trailhead on Straight Run Trail. Here you'll begin a 1000ft ascent on Deer Trail, which is a singletrack trail that ascends up the face of Mt. Nesmuk. After your climb, you'll be able stride out on Stone Road, a gradual logging across the mountain top. Turn left and head down the technical beginnings of Water Trough Trail that will turn into a 900ft descent on Horse Run Trail reaching the Canada Run aid station at mile 5.0 located on Canada Run Road.

After refueling, immediately head into the woods to the first stream crossing before heading up an old logging grade named Oil Well Hollow. You'll soon come to Bark Slide Trail, a 0.5 mile long grueling climb with 550ft ascent. Catch your breath on Matson Road before turning left onto Lost Trail as you descend back down to Oil Well Hollow. Finish your ascent up Oil Well Hollow to recover at the Baldwin Run aid station at mile 8.0 located on Baldwin Run Road.

Continue down Carpenter Trail, which is a runnable technical descent with multiple stream crossings before popping out onto Spoor Hollow Rd. Stretch out along Spoor Hollow Road and Turn Right onto Plantation Trail. Plantation Trail is a nice rolling singletrack run winding across the mountain top, only after a steep 700ft ascent properly named as "Stinger". You'll come to the intersection of Spoor Hollow Road and Baldwin Run Road, here you'll find the Stone Road Aid Station at mile 11.0 located on Baldwin Run Road.

Head down the fast paced Jim Close Trail crossing Straight Run Road and merging onto Birchstill Trail. Birchstill Trail is a scenic singletrack ascent named after old birch stills once located in the area, thus bringing you to the final Broad Ridge aid Station at mile 13.5.

Continuing across Broad Ridge, prepare yourself for the only descent, good or bad, that you may remember for the day. Frankenstein's Forehead is a 800ft technical descent into the Straight Run stream system that will have you cursing the race director by the time you reach the bottom. Here you'll find the GM25K/GM50K split, turn left onto Straight Run Trail, this is your reward for pushing yourself as hard as you did. Wind down through the scenic Straight Run Trail system crossing several streams which will depend on water levels. Turn right onto Straight Run Road a sprint to the finish!

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in Pennsylvania


2 Views Last Month
34 Since Sep 20, 2019



Porcupine Friend
Sep 20, 2019 near Wellsboro, PA
A few moments before "Frankenstein's Forehead"
Sep 20, 2019 near Wellsboro, PA
"Frankenstein's Forehead" but the picture does not do it justice.
Sep 20, 2019 near Wellsboro, PA
Trailhead sign.
Sep 5, 2019 near Wellsboro, PA


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