Located in what seems to be the "middle of nowhere," sandwiched roughly halfway in between Mount Rainier and Mount Adams, Goat Rocks Wilderness is quickly becoming a favorite backpacking and hiking destination, and the nearly 14-mile loop trail up to Goat Lake is certainly its most popular adventure.
This hiking trail offers almost everything any outdoor enthusiast is looking for: old-growth forest, waterfalls, lush wildflower meadows, extensive wildlife (e.g., Roosevelt elk, hoary marmots, mountain goats, etc.), alpine lakes, and panoramic vistas of Washington's Cascades. What protects it, however, is the 2+ hour drive from the nearest town over 5,000 people, and the extensive snow pack that only allows this trail to be accessed for a few months out of the year.
From the Chambers Lake/Snowgrass trailhead you can choose to ascend up to Goat Lake either via the Snowgrass Trail or via Goat Ridge. Obtaining an overnight camping spot at Goat Lake is a gamble based on its popularity, however, and you'll find a lot more backcountry campsite options along the Pacific Crest Trail, which is best directly accessed via the Snowgrass Trail.
Once above tree line and connected with the PCT, Mount Adams and Mount St. Helens will come into view. To get a view of giant Tahoma (Mount Rainier's original name), you'll have to venture all the way up to the Packwood Glacier. From there, you might as well hike an additional 0.8 miles up to the top of Old Snowy Mountain (7,900 feet) to get the best vistas and to appreciate the rest of the Goat Rocks Wilderness. From the summit of this hike you can return to the PCT and then onto the Lily Basin Trail to reach Goat Lake, or you can make a somewhat tricky but direct off-trail scramble.