Mount Thompson/West Ridge

Mount Thompson via the West Ridge is Grade II with class 4 and low class 5 rock.


Drive I-90 east from Seattle to Exit 52, Snoqualmie Pass. Turn left then make the first right on the paved road to the parking area of the Pacific Crest Trail (3,022 ft). 


Hike the Pacific Crest Trail north about 8 mi to Bumblebee Pass, 5,400 ft, about one-half mile past Ridge Lake. Scramble a climbers trail up and over Bumblebee Pass and down (north) into the basin directly in front of Mount Thompson.

Snow fills the basin until mid season and water is available throughout the summer. Bivy sites can be found in the western part of the basin.


From the basin, contour northwest to a notch at the base of the West Ridge, 5,960 ft where the first pitch begins starting slightly to the left, north. 

The first pitch goes straight up the West Ridge for a full pitch to a big bushy tree.

The second pitch continues straight up the ridge about 120 ft to a solid but airy belay. The third pitch continues straight up past a large ledge with a snag up to a giant slab.

The next pitch is easy walking across the top of a large slab to a corner at base of the continuation of the ridge.

Proceed straight up for one long or two short pitches to just below false summit. Scramble over false summit and one short pitch leads to the summit.


Descend via the East Ridge including one 15 ft section of Class 4 downclimbing and some tricky Class 3 slabs. Many parties rappel sections of the East Ridge with one or two short rappels. After reaching notch in ridge, descend gully to basin.


Seattle to Trailhead 1
Trailhead to Camp 4 2,500
Camp to Summit 6 1,000
Summit to Trailhead 4-6


Rack to 3 in, ice ax in early season.


  • Beckey's Cascade Alpine Guide, Vol. 1 describes a route that is partially on southwest face. The above route goes straight up the West Ridge. Finding the correct start for the climb and descent often takes longer than expected.
  • Although described in two days, many parties complete this climb round trip from the cars in one long day.
  • This peak's name is spelled Thomson on the USGS and Green Trails maps, but Thompson in most guidebooks.

FOr leaders

Permit information

As of 2017, the Snoqualmie Ranger District considers Mountaineers trips and courses to be "nominal use". Leaders should print and copy this designation letter to show rangers they may see on trail or carry a digital copy on their phone.

  • Suitable Activities: Climbing
  • Climbing Category: Intermediate Alpine
  • Seasons: May, June, July, August, September, October
  • Weather: View weather forecast
  • Difficulty: Intermediate Rock Climb
  • Length: 20.0 mi
  • Elevation Gain: 3,500 ft
  • 6,554 ft
  • Green Trails Snoqualmie Pass No. 207
  • USGS Snoqualmie Pass
  • USGS Chikamin Peak
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