Boston Peak/Southeast Face via Quien Sabe Glacier

A trip requiring both glacier and rock skills. The scenery of Boston Basin makes the challenging approach well worth the effort. Be extra careful on the rock portion of the climb as Boston Peak is notorious for its loose rock. 2-3 hr to camp; 7-9 hr camp to summit.


Drive I-5, take Exit 232 (Cook Road) at Burlington, turning east to Sedro Wooley and SR 20. Continue 47 mi to Marblemount for trip permits for Boston Basin Zone at Park Ranger Station. Continue to the Boston Basin Trailhead and park (limited parking) 3,200 ft.


Hike the Boston Basin Trail for approximately 3 mi into Boston Basin. On a warm day the stream into the basin may be full and difficult to cross. Leave early in the day to make the crossing safer. If it is too full to cross, one can ascend the moraine about 600 ft to a flat area where the crossing is safer. Camp on snow or slabs at established sites at about 6400'.


From camp continue on climber's left towards the left side of Sharkfin Tower. Rope up around 6700 ft. Make a rising traverse near the cliffs below Sharkfin to a flat portion of the Quien Sabe glacier. Pick a line up the steeper portion of the glacier avoiding crevasses. Later season, it is usually best to traverse to climber's right to end run the bergschrund, then cut up and left above the bergschrund up to the Boston-Sahale col. Unrope at the col, coiling ropes.

Follow the ridge towards Boston Peak. The ridge is initially flat, then widens onto loose rock. Stay on the right, generally following right on the crest. The ridge steepens, widens, then narrows to a knife edge (exposed class 3-4). At the high point of the ridge you will see the false summit ahead of you. Make some class 4 moves down and follow a trail along the edge of the cliff to the right (east) which leads around the false summit. You may find cairns marking this route. After about 100 ft you'll suddenly come into sight of the Boston Glacier and the summit pyramid of Boston Peak.

Cross the glacier above the bergschrund (about 200 ft), and attain a small ledge on the left just before the summit block. There may be a moat here, but usually it is manageable. Note rappel slings above you on the South Face of Boston. Climb up a few feet to a wide, downsloping ledge covered in loose stones, and follow it around the east side of Boston for about 100-200 ft to its end.

Build an anchor here and rope up for the first technical rock pitch. Follow the rock up, trending to climber's right on a series of ledges covered in small rocks and sand. After about a half a rope length, the easiest line starts to trend left. Setup a belay here.

Lead up and left less than a half rope length, up a wide chimney and encounter the crux: either a wide offwidth crack straight ahead or a rib to the right. Climb one of these features to attain the ridge, and set up a belay.

The third pitch is just an exposed scramble (class 3-4). Belay from here to the summit placing one or two pieces.


Rappel the South Face with either three 50 m rappels or a short rappel and a 60 m rappel.


Seattle to Trailhead 2.5
Trailhead to Camp 2-3 3,200 ~4
Camp to Summit 7-9 2,500 ~1.5
Summit to Trailhead 4-5 ~5.5


Ice axe, crampons, standard glacier travel gear, small alpine rack, 50 m single rope.


This is a serious climb. It is best suited for strong students and experienced leaders. The climb is more reasonable as a two day trip, but can be done as a very long day with a car camp. Consider limiting the party size to four.

Note this climb can qualify for either a Basic Glacier or Basic Rock credit.

  • Suitable Activities: Climbing
  • Climbing Category: Basic Alpine
  • Seasons: July, August, September, October
  • Weather: View weather forecast.
  • Difficulty: Basic Glacier Climb
  • Length: 11.0 mi
  • Elevation Gain: 5,700 ft
  • 8,894 ft
  • Land Manager: North Cascades National Park
    Stephen Mather Wilderness
  • Parking Permit Required: None
  • Recommended Party Size: 6
  • Maximum Party Size: 12
  • USGS Cascade Pass

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