Page Type Page Type: Mountain/Rock
Location Lat/Lon: 44.44800°N / 112.995°W
Additional Information County: Lemhi, Beaverhead
Activities Activities: Hiking, Bouldering, Scrambling
Seasons Season: Spring, Summer, Fall, Winter
Additional Information Elevation: 11141 ft / 3396 m
Sign the Climber's Log


Eighteenmile Peak 11141' is the highest peak that sits on the Continental Divide in the Beaverhead Mountains.

If you like wide open country, then Eighteenmile Peak is a destination worth considering. Forested areas are minimal and open countryside is the rule. The Harkness Lakes are a magnet for anglers and the Continental Divide Trail weaves its path through the open terrain.

There is no shortage of views in this portion of Montana's big sky country. Lima Peaks and the reddish tinted Cottonwood Mountain keep you entertained on the way up. Once on top, Bell Mountain and Diamond Peak rise up to pierce the sky in Idaho's Lemhi range. Jump Peak seems close enough to touch while Scott Peak and Italian Peak loom to the south.

This part of southwest Montana is high, remote, and sparsely populated. A handful of ranches and a few fisherman are all that separate you from an isolated backcountry experience.

Eighteenmile PeakEighteenmile Peak

Getting There


Destination: Harkness Lakes

Negatives: From I-15 it is 28.5 miles to Harkness Lakes.

Positives: 85% of the drive in is 45-50 mph road. The State of Montana has excellent signs at all the road junctions.

Directions: From I-15 take exit 23 at Dell and turn onto the Westside Frontage road. Travel 1.5 miles and turn onto Big Sheep Creek road.

Travel 17.4 miles to the first Nicholia Creek road sign. Stay left headed for Nicholia Creek. Travel 6.4 miles to the second Nicholia Creek road sign and follow it.

From here it is 0.8 miles to the first Harkness Lakes sign. Follow it and travel 1.4 miles to the second Harkness Lakes sign.

From here it is 1 mile to Harkness Lakes. Only the last 50 yards up to the lake is 4WD.

Notes:Cottonwood Creek does cross the road and you will have to drive through it and a couple of other 'water holes' on the way in.


From Hwy 28 between Leadore and Mud Lake take the Nicholia Road. After about 3 miles on this northeast running road you will come to a junction. Take a left and head north traveling about one mile through private property until reaching FS-189. Turn right onto FS-189 which is Willow Creek Road and drive to your best starting point to access Montana Canyon.

According to your Lopez (pg 330), the local ranch owner gates his private property section in the fall, so plan accordingly.

Summit Routes

From Montana
Eighteenmile Peak - northeast rampNortheast ramp

Northeast ramp

From the Harkness Lakes head cross country straight for the northeast ramp. You can actually find a well worn trail up the ramp. As the ramp tops out the rugged summit block awaits. As Lopez indicates, the peak is capped with a 'rugged quartzite summit block'. Typical Class 3 on the summit block. Most would consider it routine.

Starting elevation at Harkness Lakes: 8200'
Round trip distance: 6.8 miles

From Idaho

Route descriptions can be found in Idaho A Climbing Guide on pages 324 & 325, which are too lengthy and detailed to describe here.

To avoid the harder routes described in Lopez' book, do not gain the Eighteenmile/Jump Peak saddle.

Instead aim for the base of the summit block on its south side. There appeared to be a well beaten path this way although with a lot of loose material to contend with. This approach is up the Montana Canyon drainage. This route will actually put you on the ridge in the same place the northeast ramp places you. Lopez' routes put you west of the summit block.
Eighteenmile PeakEighteenmile Peak



This peak is very hard to resist as a second peak for the day combined with Eighteenmile Peak.

Eighteen Mile to Cottonwood RidgeThe ridge to Cottonwood

Option 1 is to down climb off of Eighteenmile's summit and follow the ridge north to Cottonwood. Expect some serious and sketchy Class 3 right away before gaining simpler terrain further along the ridge. Photo credit: bakcast.

Cottonwood MountainCottonwood Mountain
Lake 9600Lake 9600

Option 2 is to drop down the northeast ramp and aim for Lake 9600. From the lake pick your best route to gain the summit of Cottonwood.


This peak is closer than Cottonwood and if you approached from Idaho, it might be a better choice.

Option 1 would be to work your way down the southwest ridge of Eighteenmile and then gain the east ridge of Jump Peak. Expect some serious Class 3 getting off of Eighteenmile's summit and a tricky gully to ascend to gain Jump Peak's east ridge. Once on the ridge it is a walk up.

Option 2 would be to drop down into Montana Canyon and then work your way up to the east ridge of Jump Peak. You will still have to contend with the tricky gully to gain the east ridge. Photo credit: brendon.

Eighteenmile Peak, one of the...Jump Peak / Eighteenmile Peak.



There are a couple of developed camping areas along Big Sheep Creek road. Also, you can set up camp right at the Harkness Lakes.

When to Climb

This peak can be climbed in any month of the year. I suspect that winter ascents are primarily done from the Montana side.

Eighteenmile PeakEighteenmile Peak

Red Tape

There are none except for possible private land issues on the approach from Idaho.



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