The Wonderland Trail is a backpacker’s dream: 93 miles of passes, forests, streams, and alpine meadows that completely encircle the mountain. The trail has lots of ups and downs, including 3,500-foot changes in elevation in several stretches of the route.
Allow 10–14 days for the entire trip. Food (but not fuel) can be cached at ranger stations along the way by mailing packages to yourself; contact the Park Service (360/569-2211) for addresses and other specifics.
You can start your Wonderland hike almost anywhere—Mowich Lake, Longmire [1], White River, Box Canyon, or Ipsut Creek among the possibilities. A wide range of shorter one-way and loop hikes are also possible along the Wonderland Trail.
Also for marathon packers, the Pacific Crest Trail touches the east edge of the park at Tipsoo Lake on Highway 410, continuing north to British Columbia [2] and south to Mexico.
Links:
[1] http://www.moon.com/destinations/washington/south-cascades/mount-rainier-national-park/sights/longmire-area
[2] http://www.moon.com/destinations/british-columbia