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Pets allowed
Elevation Gain
4,134.00 ft (1,260.04 m)
Trail type
28.30 mi (45.54 km)
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South Fork of the Boise River Headwaters Overview

The southeastern border of the Sawtooths is not well defined. Some people consider the Alturas and North Fork of the Ross Fork drainages to be the boundary between the Sawtooth and Smoky Mountains. Others might draw the line along the divide between the headwaters of the Salmon and South Fork of the Boise River. Both definitions ignore the network of trails in the headwaters of the South Fork of the Boise River. The North Fork of the Ross Fork, Johnson, Vienna, Emma, and Big Smoky Creek drainages can be connected into a variety of long loops that are best accessed from the Sawtooth Valley.

The canyons in the South Fork of the Boise River are impressively deep with 2,000 to 3,000 feet of relief. The underlying geology, however, is predominately volcanic and sedimentary rock, so they lack the dramatic vertical walls found in the granitic heart of the Sawtooths. There are very few alpine lakes and cirques in the region. Instead, the broken rock tends to form long, sweeping slopes that drop steeply to the valley floor. Backpackers gravitate to the trails in the Sawtooth Wilderness, so these loops are more frequently explored on a motorcycle or mountain bike.

The trails in the South Fork of the Boise River are steeper and less frequently maintained. The underlying geology erodes into loose, rocky conditions, and trails can deteriorate more quickly, especially in the steeper sections. Combine this with the remote location over the divide in the headwaters of the South Fork of the Boise and you have the ingredients for adventure (and possible disaster!). Riders need to keep these factors in mind and take the necessary precautions to avoid getting stranded in this remote terrain.

This ride begins and ends at the Alturas Lake Creek Trailhead, so check out that adventure to get to the divides with Johnson and the North Fork of the Ross Fork. Other hiking or biking options in the Alturas Canyon include Alpine Creek Canyon and Eureka Gulch.

Johnson Creek to the North Fork of the Ross Fork (South Fork of the Boise River)

The Johnson to North Fork of the Ross Fork loop is accessed from the headwaters of Alturas Lake Creek and takes place primarily in the headwaters of the South Fork of the Boise River. The opportunity to see so much terrain in a single 30-mile ride is enticing. There are some great views at the head of each canyon, and early to mid-summer wildflowers can add color to the sunnier slopes. There is an old, roofless cabin located at the head of the Ross Fork Basin that is of historic interest. On hot summer days, a beautiful plunge pool in the North Fork of the Ross Fork is perfect for cooling off.

Mountain Biking

Disclaimer: this is an “adventure” mountain bike ride. While there is some great riding and long singletrack descents, the Johnson/North Fork of the Ross Loop is NOT a well-maintained, smooth, and “flowy” ride. Bikers will encounter some steep and difficult riding/hike-a-bike conditions at the head of Alturas Lake Creek. From the top you can descend in either direction. The clockwise route yields a longer singletrack descent down Johnson Creek that has some loose sections but is quite fun. The climb up the North Fork of the Ross Fork, however, is an endurance test interrupted by more than 20 dismounts into extended hike-a-bike sections. A more competent rider might be able to tackle some of the steep, loose cruxes, but it is a very challenging climb.

Reference: All content excerpted from Exploring the Sawtooths - A Comprehensive Guide by Idaho River Publications

Logistics + Planning

Preferable season(s)




Parking Pass

Not Required


Long ride covers a lot of terrain. Mid-summer wildflowers. Challenging riding.


Remote drainage. Steep hike-a-bike ascents. Motorcycle use allowed.

Trailhead Elevation

7,080.00 ft (2,157.98 m)


Backcountry camping
Historically significant
Big vistas

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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