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Sister Rocks-Observation Peak Loop Hike

From Oregon Hikers Field Guide

This page is marked as Off trail. The route or sections of the route may be dangerous and hard to follow and is not recommended for beginning hikers without an experienced leader. Beginning hikers should check out our Basic Hiking Information page.
Heading down the west ridge from the Second Sister, Sister Rocks (bobcat)
Avalanche lilies (Erythronium montanum), Observation Trail (bobcat)
Meadow boardwalk, 606 Spur Trail, Trapper Creek Wilderness (bobcat)
Basil Clark sign (below) at Rim Trail junction, Trapper Creek Wilderness (bobcat)
Mt. Adams from Observation Peak (bobcat)
The loop, with some off trail, including Sister Rocks and Observation Peak (not a GPS track) (bobcat) Courtesy: Caltopo
  • Start point: Observation Peak TrailheadRoad.JPG
  • End point: Observation Peak
  • Trail Log:
  • Hike Type: Lollipop loop
  • Distance: 8.4 miles
  • Elevation gain: 2280 feet
  • High Point: 4,268 feet
  • Difficulty: Moderate
  • Seasons: Summer into fall
  • Family Friendly: No
  • Backpackable: No
  • Crowded: No


Hike Description

The two big viewpoints in the Trapper Creek area are at Sister Rocks and Observation Peak, the former being higher and offering a more expansive vista than the latter. It’s an easy in and out to Sister Rocks from the Observation Peak Trailhead (See the Sister Rocks Hike), but the adventurous can fashion a loop by doing a little cross country down the Sister Rocks west ridge, during which you’ll pick up the remains of the east end of the Siouxon Creek Trail, hike along a gravel road, and then turn into the wilderness on an unofficial trail that begins from an abandoned road spur. The route-finding here is not difficult, and the unofficial trail has been brushed out in recent years.

Sign in at the Wilderness permit box, and head up the trail: there’s a trailside fringe of blooming avalanche lilies here in the spring. Very soon you enter old growth ridge forest of Douglas-fir, western hemlock, silver fir, and noble fir. The path undulates a little, and then rises again in silver fir forest with a bear-grass carpet. You may notice red numbers painted on some of the silver firs. You are in the Sister Rocks Research Natural Area where ongoing studies try to understand the dynamics of a silver fir climax forest. Pass a Trapper Creek Wilderness sign before reaching a rocky viewpoint on the left, which is worth a stop as it provides an excellent vista towards Mount Adams and Mount Saint Helens.

A few yards beyond the viewpoint on the ridge crest is the Observation-Sister Rocks Trail Junction. Go right here: a sign for Sister Rocks is just down the trail on a tree. Take this tread up through noble/silver for forest, drop a little, and then hike steadily up to a rock viewpoint carpeted with lichen, moss, and common juniper. Some of the view here is blocked by trees, so continue on to descend and then hike up steeply to the crest of the first of the two Sister Rocks, distinguished by its rusting pipe.

Just to the west is Second Sister, a short scramble down and up, which offers more expansive views than First Sister. Looking south, you’ll see the Trapper Creek drainage, with Howe Ridge and Observation Peak on the left and Soda Peaks on the right. Mount Hood dominates the far horizon. To the west, get a view across the Siouxon Creek drainage to Siouxon Peak and Huffman Peak. Look north and east to Mount Saint Helens, Mount Rainier, and Mount Adams. Notice also that there are three Geodetic Survey markers, used for triangulation purposes, on Second Sister!

Now begins an easy cross-country jaunt down the ridge (It’s 1 ¼ miles from Sister Rocks down to FR 58). Stay on or close to the crest of the ridge to keep on track. First, you’re descending an open slope covered with moss, lichen, and common juniper. There are good views north to Mount Saint Helens and south to Mount Hood. Then, enter Douglas-fir/silver fir forest with an open understory. Angle left up and over a mossy knoll. At the next prominence, you’ll find an abandoned trail tread to the left of the hump: This is a remnant of the eastern end of the Siouxon Creek Trail, which once ran below Sister Rocks to connect with the Observation Trail. Past the prominence, you’ll quickly run out of obvious tread, but there’s a viewpoint up to the right that offers a clear vista towards Mount Saint Helens. Traverse the left side of the next outcropping on the ridge, getting a view down to the forest bowl of the Trapper Creek headwaters. Pass at least three mysterious square pits on the ridge crest, and drop down the center of the ridge. Stay to the left of a small talus field with a skirt of vine maple. Continue down; when you see FR 58 below you, descend to it. You’ll arrive just past the pullout and small cairn that mark the Upper Siouxon Trailhead.

Go left on the road for 0.8 miles. Drop gradually through encroaching Sitka alder, and pass a spur road leading off to the right. Rise a little from a boggy area, and pass a small lake on the left. Soon, you’ll see the abandoned 606 Spur Road on the left. You’ll be following this track and then a short user trail ¾ mile to connect with the Trapper Creek Trail.

In the wet season, a small stream will be running down the road bed, and there will be a large puddle where the route levels (There’s a detour to the left). The track drops and ends. Here, the trail heads into the forest on the right. Hike a winding route through huckleberries and bear-grass, and pass a wilderness sign on a large hemlock. You’re now walking in an old-growth woodland that also includes big Douglas-firs and some silver firs. Cross a meadow on an old boardwalk, and then bridge a branch of Trapper Creek on a log. There’s another stretch of boardwalk in a huckleberry understory, and you’ll cross another branch of the creek. Pass a cedar that had some of its lower bark peeled before you reach the Trapper Creek-606 Spur Trail Junction.

Two metal diamonds on a small silver fir mark this junction. Go left, and pass a Trapper Creek Trail sign made by Basil Clark, a Mazama volunteer who crafted many of the old Trapper Creek signs in his workshop. Head up among some large Douglas-firs, and then enter a dense wood of silver fir and western hemlock. Drop to cross a creek as the trail gains quickly in altitude. Crest a ridge, and then descend past a six-trunked silver fir cluster. Drop again to cross a shallow creek to reach the Trapper Creek-Rim Trail Junction.

It’s a short distance from here to the Trapper Creek-Shortcut Trail Junction, where you’ll go right. Ascend through the bear-grass, noting a draw to the right. The trail drops to the draw, and then follows it up to the Observation-Shortcut Trail Junction. Make a right, and then, 30 yards later, turn right again at the Observation-Observation Peak Trail Junction.

Traverse up on the Observation Peak Trail #132A in silver fir, noble fir, and Douglas-fir woods. A spur left leads up an exposed rock outcrop matted with pinemat manzanita and common juniper. There are views here of Mount Rainier, Goat Rocks, Mount Adams and the crest of Indian Heaven. Back on the main trail, pass another viewpoint looking east. Reach the open area at the top of Observation Peak and take in views of the Cascades from Mount Saint Helens down to Mount Jefferson, as well as much of the Trapper Creek drainage.

To return to your vehicle, head back down the Observation Peak Trail, and make a left on the Trapper Creek Trail. Traverse a slope, and come to the four-way Observation-Trapper Creek Trail Junction (The trail on the right is a shortcut from the Big Hollow Trail). Keep along the ridge for another 50 yards to arrive at Berry Camp, where the Big Hollow Trail joins the Observation Peak Trail. Hike up the slope through the bear-grass. Where the trail levels, you’ll hear a creek running to the left. Ascend a short distance to the ridge crest and the Observation-Sister Rocks Trail Junction. From here, head down to the Observation Peak Trailhead.


The maps show the official trail system only:

  • Green Trails Maps: Lookout Mtn, WA #396
  • Trapper Creek Wilderness (USFS)
  • U.S. Department of Agriculture, Forest Service: Mt. Adams Wilderness, Indian Heaven Wilderness, Trapper Creek Wilderness
  • U.S. Department of Agriculture, Forest Service: Mt. Adams Ranger District
  • U.S. Department of Agriculture, Forest Service: Gifford Pinchot National Forest
  • National Geographic Trails Illustrated Map: Mount St. Helens - Mt. Adams

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Oregon Hikers Field Guide is built as a collaborative effort by its user community. While we make every effort to fact-check, information found here should be considered anecdotal. You should cross-check against other references before planning a hike. Trail routing and conditions are subject to change. Please contact us if you notice errors on this page.

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