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Up-and-down trail penetrates park's Cascade Corner with access to a number of impressive waterfalls.

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Point to Point

7,274' 2,217 m


6,401' 1,951 m


545' 166 m


1,248' 380 m



Avg Grade (2°)


Max Grade (13°)

Dogs No Dogs

Features River/Creek · Views

The gravel Flagg Ranch to Ashton, Idaho NFS road is sometimes closed early in the summer due to spring washouts. Check with the Targhee National Forest or at Flagg Ranch before heading out. Also, the road to the base of the dam may be too steep and rough for some cars. Finally, the Falls River ford should not be tried before mid-July. Even then its a tricky, swift, cold, 40-foot, knee-deep ford.


This 11.6-mile trail begins just south of the park at the base of the Grassy Lake Reservoir dam, on the Flagg Ranch to Ashton, Idaho NFS road (gravel), 10 miles west of Flagg Ranch. The trail ends at a junction with the Bechler River Trail, near Bechler Meadows. This up-and-down trail penetrates Yellowstone's Cascade Corner and provides access to some of Yellowstones most impressive waterfalls.

The trail leaves the dam and follows the southwest side of the Grassy Lake outlet and then the Falls River over level terrain for the first 1.1 miles. The trail then crosses the Falls River on a tricky, swift, cold, 40-foot, knee-deep ford. The southwest corner of Yellowstone is the wettest, receiving almost 70 inches of precipitation a year. The Falls River and its tributaries drain this Cascade Corner of the park. Just 15 miles downstream this river is a raging torrent over 200 feet across, rivaling even the mighty Yellowstone River. Fur trappers in the 1830s, familiar with this important Snake River tributary, named it "The Falling Fork" in recognition of its many falls and cascades.

Shortly after the ford, the trail passes the Pitchstone Plateau Trail on the right, leaves the Falls River drainage, and ascends 250 feet, then drops 130 feet, only to regain it. You are actually following an old wagon road built in the 1880s by Mormons connecting Marysville, Idaho with Jackson Hole. At the 3.5-mile mark the trail begins a steep 600-foot drop to Proposition Creek. On the way down, the trail affords nice views of the Falls River Basin to the west.

At the 4.9-mile mark the trail crosses easily forded Proposition Creek. It then travels up and over a small ridge and arrives at a junction with the Union Falls Trail, at the 5.8-mile mark. The trail continues west eventually crossing the good-sized Mountain Ash Creek at the 7.5-mile mark. Nearby are several campsites. Mountain Ash Creek was named for a beautiful rose-family shrub with clustered white flowers and bright orange-red berries named Cascade Mountain Ash.

The trail travels past the Mountain Ash Cutoff Trail at the 8.7-mile mark and continues over fairly level terrain for another 3 miles before ending at its junction with the Bechler River Trail.

Thanks to guidebook author, Tom Carter, for sharing this trail description. To learn more about visiting Yellowstone, check out his book, Day Hiking Yellowstone.


Shared By:

Tom Carter

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  4.0 from 2 votes
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in Wyoming


4 Views Last Month
1,359 Since Sep 10, 2015



Hiking along Mountain Ash Creek.
Sep 10, 2015 near Yellows…, WY
A little fording of the river on Mountain Ash Creek Trail.
Sep 10, 2015 near Yellows…, WY
Nice views of the Falls River Basin to the west.
Mar 27, 2016 near Yellows…, WY
Taking a quick break on Mountain Ash Creek Trail.
Sep 10, 2015 near Yellows…, WY
Ford across the Falls River in late August.
Mar 27, 2016 near Yellows…, WY
Mountain Ash Creek Trail.
Sep 9, 2015 near Yellows…, WY



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