The closest Forest Service campground is the Clear Creek Campground (four miles south of town on Forest Rd. 20, 518/885-3639 or 877/444-6777, www.recreation.gov [1], $12, $9 extra reservation fee).
Squire Creek County Park (four miles west of Darrington on Hwy. 530, 360/435-3441, $15) offers year-round camping amid old-growth Douglas fir and cedar trees. The park is also home to the largest cottonwood tree in Washington.
Sauk River County Park (seven miles north of Darrington on Sauk Valley Rd., free) has more campsites. There is no drinking water.
Links:
[1] http://www.recreation.gov