Wilderness preservation is strongly supported by the American people (Cordell et al. 1998) and a substantial portion of the public domain has been allocated to wilderness. The Wilderness Act of 1964 and more than 135 subsequent wilderness bills have created a National Wilderness Preservation System of 661 wilderness areas with a total acreage that exceeds 106 million acres. The proportion of the United States currently designated as wilderness is 4.5%. Designated wilderness constitutes more than 16% of lands owned by the federal government, 57% of National Park Service lands, 22% of Fish and Wildlife Service lands, 18% of Forest Service lands and 2% of Bureau of Land Management (BLM) lands. Moreover, wilderness acreage is likely to increase substantially in the future.