Photo: Commonwealth Basin's meadows from the PCT.
If you look carefully (or if you have an old quad map) you can find the abandoned trail leading to Commonwealth Basin from the Pacific Crest trailhead on the north side of I-90 on Snoqualmie Pass. This was once a popular hiking and pack trail because it was an easy trip into the wilderness. There are some green meadows in the basin, with a creek and some nice campsites. There's not much more to be said for this trail, which was rendered obsolete by the Pacific Crest Trail. Much of the way you're within view or earshot of I-90, but you leave that behind as you reach the basin.
If you can't find the old trail, follow the PCT north toward Kendall Katwalk, but bear left after 2 miles on an unmarked trail. In less than a mile you'll cross Commonwealth Creek and enter the basin. The hike is still easy, but not easy to find, so don't try this trail unless you're comfortable with map and compass. The Creek runs year-round, and there are several tent sites among the meadows, deer and bugs.
Note: This is backcountry wilderness travel. Any trail can become very dangerous in winter conditions. You are responsible for informing yourself of the hazards and taking the necessary precautions. Please read Terms of Use.