Initially this is the same as the Sickle Couloir Approach. Start at the Redfish Lake Lodge Backpackers parking lot and take the Fishhook Creek Trail until it's end. There's a spectacular view near the pond just before this point. Horstmann is clearly visible from here and the route is basically the right side profile. From the end of the trail, make your way through an overgrown and often swampy valley. Cross to the south side of the Valley about 1/2 mile after the trail ends. Make your way past the South Face approach valley and after about 1 mile cross back across the creek to the north side of the valley and after about 2 more miles you'll see a very small unamed lake at about 8,000 feet. At this point you should be under (just north) of the route.
Since your in front of the profile route, it won't be very obvious and it's extremely easy to get onto other routes here given the complexity of the mountain and the few that have climbed it (leaving no evidence: pitons, cairns etc.). You'll need to have an alpine style mentality and good route finding. The climb is a series of pitches that end on top of towers that require small down climbs or short rappels. Then proceed up the next tower. There are at least 4 towers to go up and over, depending on your route finding. The climbing varies wildly from Class 4 to 5.9 and the rock also does. The day we climbed it was very cold and windy on the north side of this mountain. Each tower that ascend is like a false summit- we thought we were near the top at fisrt and we were only 60% of the way there after 4-5 hrs of rock climbing. You may be able to get on easier terrain to the left (east) and simul-climb, if your short on time. Eventually you'll reach the summit ridge which is Class 3-4 and contains a very historic (at least locally) summit cannister. The best descent is to take the South Face route down (no rappelling required). A rappel down the Northwest Buttress would take at least 5 double ropes and several new anchors. Look for mountain goats near the summit and on the South Face descent.
1) A double rope is recommended in case you need to rap off prematurely
2) A full trad rack with 1 set of nuts, a set of cams of all sizes
3) Lots of runners including doubles since the route wanders and you could get rope drag
4) Warmer clothes than the weather since your on the north side
5) I would recommend a brain bucket since the rock can be loose in spots, although you don't have to ever worry about aother rock climbing parties (ahhh.. Sawtooth Climbing)
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