Round Trip-11.5 miles & 4,500-ft
Starting at the Pitkin Lake TH at 8,500-ft, locate the nice trail and follow it 2.34 miles to the first the set of waterfalls at 9,920-ft. “Outpost Peak’s” steep, and rugged east slopes will be on your left and you can also make out the grassy, steep slopes of “Mount Solitude” up to the right. Continue on good trail another mile to the second set of waterfalls at 10,470-ft. The trail will relent a bit after the second set of falls. After another half mile of hiking there are some great campsites to be had in this marshy, flat area. Continue another .6 mile to Pitkin Lake, the lake is above tree line and “West Partner” is the high mountain that towers over the lake to the north, its about 4.3 miles and 2,800-ft from the TH to the lake.
For the mile long south ridge, locate the tundra covered slope to the left that ascends to the low point or saddle that connects “Outpost Peak” to “West Partner,” you can see a faint trail about a third of the way up this slope. Hike up this slope and reach the ridge-crest at 11,970-ft. Enjoy the views of Booth Lake Basin and “The Spider.” Between you and the summit lies one mile of class 3 and 4 ridge.
Begin picking your way up and over some minor rock towers (class2+ & 3,) you can bypass some of these towers by dropping to the left or the right. After about a half mile you will ascend Point 12,215-ft and descend down to another obvious saddle at 12,177-ft. The remainder of the route becomes a class 3 and 4 scramble for another half mile to the summit.
From here it is best to stay on the ridge crest, which features many rock towers with solid handholds. At about 12,700-ft, the ridge will feature a deeply inset notch. Climb as far as you can, almost to the top of the ridge (class 3.) From here you can peer down, to the left, and see where you need to get; this is also the spot to look down the west side of the ridge and locate a steep, exposed 2-ft wide ramp that descends down into the notch. Locating this ramp is key for getting around this notch in the ridge.
Descend the ramp and make an easy class 4 move off of the ramp and into a steep, dirt gully that you can ascend a few feet to the low point in the notch. Now you must climb the slabby headwall back up to crest of the south ridge. This headwall is steep class 3 with a few easy class 4 moves. Once on the crest again, continue on to the rock outcropping that is the high point of the mountain when viewed from Pitkin Lake (exposed class 3.) The true summit is only .18 mile away. At this point you can drop down and bypass most of the difficulties all the way to the summit, but we recommend staying directly on the crest.
“West Partner” has a double summit, both equally high. If you stay on the crest, it will take you to the south summit, which is the more difficult to reach. From the south summit, attaining the north summit is an easy class 2 hike.
For the descent, retrace your route back down to the saddle at 12,177-ft. From here, I recommend dropping down into upper Pitkin Lake Basin. There may be few other spots to descend from the ridge before the 12,177-ft saddle but it may cliff out in spots below.