Matternought Peak certainly does not stand out among the Teton Range from the valley floor. In fact, even from Taminah Lake, very near it's base, it is difficult to discern the actual summit. The name references this obscurity as well. In reality, Matternought is an unremarkable spire adorning the southeastern flanks of the mighty South Teton. Yet there is still one very compelling reason to visit this seemingly uninteresting little summit. And that reason is the Taminah Arete (III 5.9). Stellar moderate climbing, interesting route finding and tremendous setting make this peak worth a visit.
Please refer to Alan Ellis' exemplary Grand Teton page for logistics involved in getting yourself to Jackson Hole. I could not live up to his thoroghness, so I defer. The starting point is the Taggart Lake trailhead, just a few miles into the park from the Moose entrance station. This is a popular day use area, so expect some traffic and possible parking difficulties in full tourist season.
Follow the Taggart Lake trail, taking the first right and crossing Taggart Creek. After about 1.1 miles, take the Bradley Lake trail (right fork again) for another quarter mile, then move cross country back toward Taggart Lake, regaining a maintained trail. Hike North toward the moraine separating Bradley and Taggart Lakes. On the open slope of the moraine, at about 6,960 feet and before the first switchback, find a faint trail to the left. This trail leads into Avalanche Canyon, and is easier to follow once around the lake. Stay as close to the bottom of the canyon as possible, while still avoiding numerous marshy spots. Keep a keen eye out for moose in this forest, there are quite a few. At the fork of Taggart Creek, just below Shoshoko Falls, follow the talus cone North of the falls until it is possible to traverse to Lake Taminah. There is spectacular camping here, and it is close enough to Matternaught to make it worth stopping. There is a campsite further up, a small green spot that will accomodate a small party.
Approaching Taminah Arete
From the west shore of Taminah Lake, follow talus up and left (west), beneath a large face (Dem Bones III 5.10), heading for a break in the lowest rock band at the left edge. If you miss this break, it is also possible to traverse past Matternought Peak and switchback to the base of the formation on a broad talus ledge. Taminah Arete will be obvious from this angle. Scramble back up on the east side of the ridge to the base of an orange wall with a thin crack in a short corner that marks the beginning of the route.
Campsites at Taminah Lake offer a decent view!
Approaching the East Ridge
This route is the descent for climbs originating at Taminah Lake. Follow the very large talus slope above the lake that leads to a cirque below Cloudveil peak. On the west end of this cirque is a couloir that rises to the notch between Matternought Peak and Gilkey Tower. Follow this couloir until it is possible to move left onto slabby (possibly snow covered) ledges. Follow the ledge across and up to the base of the East Ridge.
From the summit, downclimb approximately 300 feet toward the East Ridge. This is very exposed and steep. Along the crest of the ridge, a rappel point will be encountered. One double rope rappel will get you to the base of the East Ridge. Follow the serious slabs north to the large couloir, and descend this to Taminah Lake. This descent involves some non-trivial down-climbing, so don't let your guard down. If you do not summit after a climb of Taminah Arete, you should simply traverse right and downclimb to the rappel point. If you summit, do not attempt to rappel north into the obvious notch unless you intend on climbing the Sunrise Ridge route to Gilkey Tower. The rappel off of the north is not preferred, but you will find slings in more than one place.
Camping in Avalanche canyon requires a permit, available from the Jenny Lake Ranger station (307) 739-3343. Permits must be obtained in person no sooner than 48 hours before your departure. The NPS uses a quota system for camping in certain zones. With so few sites around Taminah, they can fill quickly. Get to the Ranger Station as early as possible (they open at 8 AM). You are not required to register as a climber. No fires, pets, firearms allowed in Grand Teton National Park. Be sure to bring a license plate number to the Rangers if you plan on leaving a car at the trailhead.
For route conditions, the best source of current information is the Jenny Lake Ranger station (307-739-3343). They generally begin operation after Memorial Day and continue through September. Outside of those dates, the Moose Ranger Station will have permits, but not detailed climbing information.