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Pets allowed
Not Allowed
Elevation Gain
696.00 ft (212.14 m)
Trail type
9.60 mi (15.45 km)
Please respect the outdoors by practicing Leave No Trace. Learn more about how to apply the principles of Leave No Trace on your next outdoor adventure here.

Middle Fork of the Boise River Overview

The Middle Fork of the Boise River carves a massive canyon on the east side of the Greylock and Blizzard Mountain Massif. With nearly 4,000 feet of vertical relief, the Middle Fork of the Boise River canyon is second only to the neighboring Queens River canyon in overall depth. While the scenery up the canyon is stunning, the views from the bottom never really provide a satisfying perspective of the high peaks above.

The route up the Middle Fork and over Mattingly Divide was a major transportation corridor between Atlanta and the mining towns in the Salmon and Big Wood river drainages. Ore was occasionally shipped over the pass from the Salmon River mines on and down to the Buffalo Mill on the Atlanta Hill for processing. Amazingly, a road extended up the canyon as far as La Moyne Creek in the 1920s. When the mines up that creek didn’t produce, the road was allowed to fade back into the landscape.

The lower canyon to Mattingly Junction is a good out-and-back for day hikers coming visiting the Atlanta.  It also provides access to the Leggit Lake and the Mattingly Creek adventures.  Upstream of Mattingly Junction, the trail climbs nearly 10 miles to Spangle Lake and the Ingleborg Divide with the South Fork of the Payette River.  It also accesses additional adventures up tributaries to Timpa Lake and Camp Lake

Powerhouse Trailhead to Mattingly Junction

For the first few miles, the trail winds through dense forest out of sight of the Middle Fork of the Boise River. Above the wilderness boundary, the trail avoids the Lynx Creek Gorge by climbing onto bedrock terraces carved into the canyon walls by passing glaciers. The exposed knobs along this section of the trail offer some great views of the canyon as well as a few small bivvy sites.

Swimming Holes and Waterfalls

There is a great swimming hole to start or finish your hike. It is best accessed by continuing from the trailhead to the end of the Powerplant Campgound and then following an old road and trail to the edge of the river. The waterfall at the bottom of the Lynx Creek Gorge can be accessed by leaving the trail when it starts to climb above the river. Scramble off-trail up the east side of the Middle Fork until you reach the bottom of the Lynx Creek Gorge.

Mountain Bikes

Bikes are allowed along the first 2.4 miles of easy and fun riding to the wilderness boundary. This effectively cuts 5 miles off any day hikes or off-trail explorations up the canyon. 

Off-Trail Hiking

At first the intimidating walls of the Middle Fork Canyon seem impenetrable. Further reconnaissance from neighboring ridgelines and the eye-in-the sky Google Earth camera reveal a number of possible routes for ambitious off-trail hikers. What appear to be steep but reasonable Class 3 routes up either side of the Leggit Lake cirque would allow a circumnavigation of that canyon exceeding 11 miles. It is possible to descend Peak 9,694 above Leggit Lake down its long northwest ridge to the Atlanta valley. The easiest route up Greylock Mountain is via the west ridge, but one could envision a route up the Lynx Creek Canyon from the road on the north side of the river.

The traverse from Greylock to Blizzard covers a lot of Class 2 and easy Class 3 terrain in an awesome position above both the Middle Fork and Queens Rivers. Descend the east side of Blizzard or continue all the way to Rock Creek over Point 9,364. Though the long traverse up the south ridge of Peak 9,266 might devolve into a maze of towers, the 1,400-foot climb up slabs and open ridge to Point 7,450 offers a stunning vista from a perch in the middle of this stunning canyon.

Wilderness Regulations

Most of the trail lies within the Sawtooth Wilderness. Please observe the following  regulations:
• Mountain bikes are not allowed past the wilderness boundary.
• Self administered wilderness permits are required and available at the trailhead.
• Dogs must be on a leash between July 1 and Labor Day.
• Camp 100 feet from trails, lakes and streams.
• Pack out all garbage.
• Human waste should be buried and well disguised in a cat hole 6 to 8 inches deep. Pack out all toilet paper.
• Campfires allowed ONLY in a backcountry pan or fire blanket.
• Campfires are NOT allowed at some lakes and in some drainages in the Sawtooths.  Please review the campfire restrictions at individual trailheads.
• Permits required for all stock use in the wilderness. No grazing allowed in the Salmon River watershed (This includes the Alpine Lake drainage).
• No equine stock at Edith Lake. ALL stock prohibited in the Goat Creek and Alpine Creek (Alturas Lake) drainages.

Logistics + Planning

Preferable season(s)




Parking Pass

Not Required


Swimming hole at trailhead. Glacial U-shaped canyon. Lynx Creek Gorge. Canyon overlooks.


Atlanta/Powerhouse Trailhead is remote. No major destination.

Trailhead Elevation

5,220.00 ft (1,591.06 m)


Backcountry camping
Big vistas
Geologically significant

Suitable for




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Our mission is to inspire adventure with beautiful, comprehensive and waterproof map-based guidebooks.  Owner, publisher, and photographer Matt Leidecker, grew up exploring and guiding on the rivers in central Idaho.  His award winning Middle Fork of the Salmon River – A Comprehensive Guide is the standard by which other river guidebooks are measured.  Printed on virtually indestructible YUPO paper, IRP guides are truly unique all-in-one resources for adventure.  Each book is loaded with full-color maps, stunning photographs, and information on the history, geology, and wildflowers.  Visit Idaho River Publications to explore our guidebooks to the Rogue River in Oregon and the mountains of Central Idaho.

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