UN 13,091 is sequenced with UN 13,106. One way mileage and elevation gain are measured from the summit of UN 13,106. Round-trip mileage and elevation gain assume completion of the sequence.
From the summit of UN 13,106, walk NE along the almost flat summit ridge for about .75 mile until you can drop down to the east, avoiding a minor cliff (or early season a snow cornice) and reach the broad, tundra saddle at 12,500 ft. From the saddle hike ESE gaining about 400 feet elevation on more tundra to reach the elevation marker of 12,893 on the USGS map. Continue directly east on even more tundra toward the summit, located on a small, flat plateau. If you stay directly on the ridge, you'll be on some rubble for a while followed by a short Class 2 cliff that rings the plateau. Once on top, locate the high spot and cruise the tundra over to it.
Like UN 13,106, this summit offers a commanding view of the Nellie Creek drainage. Off to the east is Crystal Peak, a high 12er that offers a nice hike from lower down on the Nellie Creek road. To descend, either retrace your ascent route or try the following: For a shorter return route, retrace your path along the ridge to the west and drop back down into the separating valley between UN 13,091 and UN 13,106. Then climb up through some large boulders and gain a shelf that leads to the south, below the summit ridge of UN 13,106. Contouring just below 12, 800 ft on elk trails, drop southwest into a steep drainage that leads directly down to the trail head. This descent is not too difficult, but definitely steep. With a little care, we arrived back safely at the car by mid afternoon after having hiked UN 13,158, UN 13,106 and UN 13,091. Taking this short cut back to the TH will save a little over 2 miles of hiking. The round-trip mileage provided reflects taking the short cut.
Links to other information, routes & trip reports for this peak that may be helpful.