The Forest Service operates 16 campgrounds (518/885-3639 or 877/444-6777, www.recreation.gov [1], generally open Memorial Day to mid-September, $8–14, $9 extra reservation fee) along the Mountain Loop [2]. Free dispersed camping is allowed on Forest Service lands away from the developed campgrounds.
From Granite Falls [3], neighboring Turlo and Verlot campgrounds are near the Verlot Service Center, while Gold Basin Campground is 2.4 miles east of the service center. Gold Basin also features an amphitheater where Saturday night campfire programs are presented in the summer. Across the road is a short, wheelchair-accessible interpretive trail.
Continuing on from Verlot, other campsites include Boardman Creek Campground (open all year), six miles east; and Red Bridge Campground, seven miles east.
From Darrington [4], Forest Service campsites include Clear Creek Campground, four miles south, and Bedal Campground, 18 miles south, both open year-round. A mile east of Bedal Campground on Forest Road 49 is a quarter-mile path to the base of spectacular North Fork Sauk Falls, where the river plunges 45 feet.
From Darrington via Suiattle River Road No. 26, Buck Creek Campground, 22 miles northeast of town, features a quiet riverside setting in an old-growth forest. Sulphur Creek Campground, 28 miles from Darrington (near the end of Suiattle River Rd.), is just a mile away from the Glacier Peak Wilderness [5] and is open year-round. A short trail leads from the campground along Sulphur Creek to colorful pools containing rather odoriferous hydrogen sulfide gas. See Darrington [6] for other camping options.
Links:
[1] http://www.recreation.gov
[2] http://www.moon.com/destinations/washington/north-cascades/mountain-loop-hwy
[3] http://www.moon.com/destinations/washington/north-cascades/mountain-loop-hwy/granite-falls
[4] http://www.moon.com/destinations/washington/north-cascades/mountain-loop-hwy/darrington
[5] http://www.moon.com/destinations/washington/north-cascades/mountain-loop-hwy/recreation/hiking/glacier-peak-wilderness
[6] http://www.moon.com/destinations/washington/north-cascades/mountain-loop-hwy/darrington/camping