Located in the eastern portion of Mount Rainier National Park, Tamanos Mountain offers unimpeded, up-close views of Mount Rainier's eastern slopes. The rugged Chimney peaks that skirt off of Mount Rainier toward the southeast add to the scene. Distant waterfalls can be heard along with the occasional rock slide in this massive bowl of peaks.
Park in a designated turnout along the road to Sunrise for the Owyhigh Lakes Trailhead (on the south side of the road). The hike to the summit of Tamanos Mountain begins along several switchbacks that through dense forest until the trail plateaus in the Owyhigh Lakes basin. There are many designated backcountry campsites in this area. Many wildflowers can be seen in the right season as the timberline dwindles to reveal an expansive, sloping meadow to the west, the top of Tamanos being the terminus of this meadow.
After passing the Owyhigh Lakes to the south, follow the unmarked trail to the right at a junction. The trail at the northwest end leads up the steep meadow to the summit. At this point the trail becomes overgrown and clearly less used. Make your way through the meadow to the obvious saddle, the high point to the northwest. Enjoy expansive views to the south toward Mount Adams and the Goat Rocks, and you'll be greeted by an incredible view of Mount Rainier just a few short miles to the east with Little Tahoma hiding in the foreground. There are a few clearings on this ridge that could be backcountry campsites. Traverse up along the ridge to reach the false summit. Climbing Tamanos to its true summit involves some rock scrambling up fairly loose rock to the adjacent spire. Be cautious and sure of your handholds and footing. Enjoy a lunch while taking in the amazing views of Mount Rainier, and (on a clear day) views of Glacier Peak and Mount Stuart to the north can be had.
Return down the steep meadow to the main trail along the Owyhigh Lakes and down through the forested switchbacks leading to your vehicle. If you are hiking in a large group off-trail, remember to spread your group out so as not to create a new trail, and practice the Leave No Trace principles.