Located halfway between Mount St. Helens [1] and the Columbia River and covering just 6,050 acres, Trapper Creek Wilderness is one of the smaller wilderness areas in Washington. It is also one of the few places in this part of the state where the forests have been spared from logging.
Several trails provide access; longest is the Observation Trail (No. 132), which takes you through dense old-growth stands of timber, across a ridge, and to a spur trail that edges up 4,207-foot Observation Peak for panoramic views.
From here, you can continue down to the junction with Trapper Creek Trail (No. 192), which takes you back along this pretty creek to your starting point. This loop hike is approximately 12 miles long. Call the Mt. Adams Ranger District (509/395-3400) for details.
Links:
[1] http://www.moon.com/destinations/washington/south-cascades/mount-st-helens-national-volcanic-monument