Koosah Mountain is a bump along the Pacific Crest Trail in Three Sisters Wilderness. Just south of the lakes basin around Sisters Mirror Lake, Koosah Mountain is a short add-on to get the heart rate up on this relatively easy trail. It is also one of the few spots along this hike that will get you a good view of the surrounding mountains.

There is a nice rocky outcropping with a view towards Mt Bachelor and the Three Sisters just below the summit. While there is no trail to the actual high point of Koosah Mountain, it is an easy little walk up from behind the outcropping. The view from the outcropping is better.

During the summer you’ll likely pass a lot of Pacific Crest Trail through-hikers. I hiked this on August 5 and ran into at least eight of them while I was lounging around the Koosah Mountain view point. I wish I had carried in some goodies to share!

Topo map and GPX track:


In and out hike on well marked trail. This hike could be done as a dayhike, or as a short backpack to Sisters Mirror Lake basin.


10.75 miles round trip

Elevation Gain:

+/- 1200 ft

Trailhead and Permit Notes:

Koosah Mountain is accessed via the Sisters Mirror Lake trailhead along the Cascade Lakes Highway. The trailhead has room for about 10 cars, and has a pit toilet. Northwest Forest pass or equivalent is required.

At approximately 3.5 miles in, the trail meets the PCT. Head south, passing Sisters Mirror Lake, and up to Koosah Mountain. There is a nice viewpoint with a rocky outcropping just below the summit. For peak purists, the actual summit is a short cross-country diversion. The view is best from the outcropping.

Useful Guides and Gear:

Rebecca Sowards-Emmerd

Mountain sports addict. Dog Mom. Craft beer drinker. Tech nerd. The best days are those spent above 10k ft. Meet me on Twitter, Facebook, or Google +


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