Wonder Mountain Wilderness is roughly triangle-shaped. A high ridge encompasses the southern point of the triangle, rising to the peak of 4,848-foot (1,478 m) Wonder Mountain. Below the summit stands a heavy forest of western hemlock, Douglas fir, and silver fir. Alder, willow, and vine maple grow along McKay Creek and Five Stream, both of which have their headwaters in the wilderness. huckleberry and thimbleberry are also common.[1][2]
There are no trails leading into or through Wonder Mountain Wilderness. Two forest roads that run near the southeast and southwest borders are closed to motor vehicles from October to May to provide protection for wildlife. The southeast road has been permanently closed at the lake Cushman bridge for years about ten miles from the base of wonder mountain. The wilderness starts at the top of the ridge line. This route is not accessible. [1][2][4]