Pitch your tent or park your trailer at one the convenient Forest Service campgrounds in the Mount Baker-Snoqualmie National Forest.
Situated along the South Fork of the Snoqualmie River, Tinkham Campground (exit 42 off I-90, drive east on Tinkham Road 55 for 1.5 mi., 541/338-7869, www.recreation.gov [1], $14–16) is a favorite among local Scout troops who’d like to get out in the woods but don’t want to get too far from civilization.
Same goes for Denny Creek Campground (exit 47 off I-90, take left and go under freeway then follow signs to campground 3 mi. away, 541/338-7869, www.recreation.gov [1], $18 tent, $24 RV), which sits in a valley under the I-90 overpass high above.
Tinkham welcomes small RVs but has no hookups, and Denny Creek has electric-only hookups. Both sites are located near a bunch of great trailheads, including the Denny Creek Trail, which leads to some fun natural water slides only a mile away from the campground. Both sites also offer a couple of barrier-free campsites. Both are open May–September.
Links:
[1] http://www.recreation.gov