There are so many of them. There are degrees of near-deserted of course. The Alpine Lakes Wilderness, for example, is popular but less so than the popular areas of Rainier. Mount Adams Wilderness. Much of the Mt. Baker-Snoqualmie National Forest. But really, just look at a map of the Cascades and see the vast swath of national forest land there and pick up a Washington hiking guidebook to provide some pointers.