Forbidden Peak/Northwest Face of North Ridge

This is a very esthetic route combining an ice climb with the enjoyable rock of the upper North Ridge. This is a strenuous climb in an incredible setting! At Grade III 5.6-5.7, this is an ice or steep snow climb for those with some experience.

Getting There

Drive to Marblemount on SR-20. Register at the Marblemount Ranger Station. Take the Cascade River Road (Forest Road 15) for 21.7 miles to the Boston Basin Trailhead, a pull out just before the Cascade Pass Trailhead.


The trail initially follows the old Diamond Mine Road bed for about 1 mile to where the trail leaves the road sharply right and steeply up. Follow trail to Boston Basin. Either camp high in Boston Basin, off the meadows and on rock or snow, at designated upper campsites (6,400 ft) or camp on the flat bench (7,500 ft) below Sharkfin Tower, beside the Quien Sabe Glacier. You can also bivouac on the snow when crossing over the northeast ridge (called the “North Ridge") at about (7,700 ft).

Ascent Route

From Boston Basin, ascend the moraine and move along west edge of the Quien Sabe Glacier to 7,500 ft. Climb to Sharkfin Col (7,720 ft), the low point on the ridge and left of Sharkfin Tower, via 10 feet of 5.7 rock climbing and 200 feet of Class 3 gully. Rappel 150 feet down a loose gully from the Col to the Boston Glacier. Descend in a northward traverse through crevasses to 7,000 ft, passing a rock buttress. Then traverse, ascending to the north end of the Boston Glacier and cross over the northeast ridge (called the “North Ridge") at ~7,700 ft. This might be a better place to bivouac.

Descend to the north arm of Forbidden Glacier, near the base of an ice face. A large crevasse can open at 7,600 ft, slowing progress. Climb 30 to 40+ degree snow and ice on the Northwest Face 900 feet to the crest of the North Ridge’s upper section, then climb on to the summit. The icy face is composed of two ice sections divided by a narrow rock band. The upper section ends at the cornice at mid-ridge (~8,375 ft). Once on the ridge the firm rock can be climbed on or near the crest to the summit.

Descent Route


Trailhead to Camp 4-5 3,300
Camp to Summit 10+ 2,300
Summit to Trailhead 4+ -2,300
Camp to Trailhead 2.5 -3,300


Standard alpine ice climbing gear.


  • This wonderful North Cascades ice climb has a remote feeling and a circuitous spectacular route, but is not a good choice for a first ice climb.
  • Rapid efficient travel and equanimity with exposure are key.
  • Consider impact in Boston Basin when choosing a campsite.
  • Intermediate Mountaineering credit before July 1, Ice credit after July 1.
  • The camp to summit time are largely dependent upon crevasse conditions.
  • Permits are required for camping and can be difficult to obtain. Obtain permit at the ranger station in Marblemount.
  • Suitable Activities: Climbing
  • Climbing Category: Intermediate Alpine
  • Seasons: July, August, September
  • Weather: View weather forecast
  • Difficulty: Intermediate Ice Climb
  • Length: 7.0 None
  • Elevation Gain: 6,200 ft
  • 8,815 ft
  • Land Manager: North Cascades National Park
  • Parking Permit Required: None
  • Recommended Party Size: 6
  • Maximum Party Size: 6
  • Maximum Route/Place Capacity: 12
  • USGS Forbidden Peak
  • USGS Cascade Pass
  • Green Trails Cascade Pass No. 80
  • Green Trails Diablo Dam No. 48
  • Green Trails North Cascades Ross Lake No. 16SX
  • Trails Illustrated North Cascades National Park
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