T he Wilderness Act of 1964 (P.L. 88-577, 16 U.S.C. §§1131-1136) established the National Wilderness Preservation System as a system of undeveloped federal lands, which are protected and managed to preserve their natural condition. The act initially designated 54 wilderness areas containing 9.1 million acres of federal land within the national forests. Since then, Congress has passed more than 100 subsequent laws designating additional wilderness areas. As of September, 1, 2017, the National Wilderness Preservation System totaled 765 areas, spanning nearly 110 million acres. Many believe that certain areas should be designated to protect and preserve their unique value and characteristics, and bills are usually introduced in each Congress to designate wilderness areas. Others oppose such legislation because commercial activities, motorized access, and roads, structures, and facilities generally are prohibited in wilderness areas. Another area of concern is how prohibition of such activities can affect law enforcement in wilderness areas along U.S. national borders. This report presents information on wilderness protection and a discussion of issues in the wilderness debate—some pros and cons of wilderness designation generally; proposed legislation; and a discussion of wilderness study area designations and protections and related issues. This report is updated periodically to track the status of legislation introduced in the 115 th Congress to designate new wilderness (see Table 1 ) or to release wilderness study areas (WSAs; see Table 2 ). Tables of legislation from the 114 th Congress are provided in the Appendix of this report. In the Wilderness Act, Congress reserved for itself the authority to designate federal lands as part of the system. This congressional authority is based on the Property Clause of the Constitution, which gives to Congress the "Power to dispose of and make all needful Rules and Regulations respecting the Territory or other Property belonging to the United States." Wilderness areas are part of existing units of federal land administered by the four federal land management agencies—the Forest Service (FS), in the Department of Agriculture; and the National Park Service (NPS); Fish and Wildlife Service (FWS); and Bureau of Land Management (BLM) within the Department of the Interior (DOI). Thus, statutory provisions for these agencies' lands, as well as the Wilderness Act and subsequent wilderness statutes, govern the administration of the designated wilderness areas. Wilderness designations can be controversial because the Wilderness Act (and subsequent laws) restricts the allowed uses of the land within designated areas. In general, the Wilderness Act prohibits commercial activities, motorized access, and roads, structures, and facilities in wilderness areas. Specifically, Section 4(c) states: Except as specifically provided for in this Act, and subject to existing private rights, there shall be no commercial enterprise and no permanent road within any wilderness area designated by this Act and, except as necessary to meet minimum requirements for the administration of the area for the purpose of this Act (including measures required in emergencies involving the health and safety of persons within the area), there shall be no temporary road, no use of motor vehicles, motorized equipment or motorboats, no landing of aircraft, no other form of mechanical transport, and no structure or installation within any such area. This section thus prohibits most commercial resource exploitation (such as timber harvesting) and motorized entry (with cars, trucks, off-road vehicles, aircraft, or motorboats) except for "minimum requirements" to administer the areas and in emergencies. However, Section 4(d) provides numerous exceptions, including (a) possible continued use of motorboats and aircraft where uses are already established; (b) measures to control fires, insects, and diseases; (c) mineral prospecting conducted "in a manner compatible with the preservation of the wilderness environment"; (d) water projects; (e) continued livestock grazing; and (f) certain commercial recreation activities. Subsequent wilderness statutes have included additional provisions for administering those individual wilderness areas, including exceptions to the general Wilderness Act prohibitions. Existing private rights established prior to the designation of an area as wilderness remain in effect, unless expressly modified by the wilderness statute. The designation does not alter property rights, but does not suggest that all uses prior to the designation are allowed. There must be a property right, rather than a general right of use. Courts have consistently interpreted the phrase "subject to valid existing rights" to mean that the wilderness designation is not intended to take property in violation of the Fifth Amendment of the Constitution. Ownership of land within a wilderness area would confer existing rights. While most uses—timber harvesting, livestock grazing, motorized recreation—are not considered as rights to the lands and resources, the mining and mineral leasing laws do provide a process for establishing rights to the mineral resources. The Wilderness Act allowed implementation of these laws through 1983 for the original areas designated; many subsequent laws explicitly withdrew the designated areas from availability under these laws. Wilderness designations are permanent unless revised by law. Congress has statutorily removed lands from several wilderness areas, commonly to adjust boundaries to delete private lands or roads included inadvertently in the original designation. Lands do not have to be untouched by humans to be eligible for statutory designation as wilderness. Specific statutes designating wilderness areas may terminate or accommodate any existing uses or conditions that do not conform to wilderness standards (commonly referred to as nonconforming uses ). Many previous wilderness designations have directed immediate termination of nonconforming uses, whereas other bills have directed the agencies to remove, remediate, or restore nonconforming conditions or infrastructure within a specified time frame. Alternatively, many nonconforming uses and conditions have been permitted to remain in designated wilderness areas. The Wilderness Act explicitly allows continued motorized access by aircraft and motorboats in areas where such uses were already established. The Wilderness Act also permits motorized access for management requirements and emergencies, and for fire, insect, and disease control. Numerous wilderness statutes have permitted existing infrastructure (e.g., cabins, water resource facilities, telecommunications equipment) to remain and have authorized occasional motorized access to operate, maintain, and replace the infrastructure. A few statutes have also allowed new infrastructure developments (e.g., telecommunications equipment and a space energy laser facility) within designated wilderness areas. Although such authorizations are usually for a specific area, some statutes have provided more general exemptions, such as for maintaining grazing facilities or for fish and wildlife management by a state agency in all areas designated in the statute. Various existing wilderness statutes have included special access provisions for particular needs. For example, several statutes have included provisions addressing possible military needs in and near the designated areas, particularly for low-level military training flights. Similarly, statutes designating wilderness areas along the Mexican border commonly have allowed motorized access for law enforcement and border security. (See " Wilderness and U.S.-Mexican Border Security " below.) Other statutes have contained provisions allowing particular access for tribal, cultural, or other local needs. Several statutes have included provisions authorizing the agencies to prevent public access, usually temporarily and for the minimum area needed, to accommodate particular needs. Proponents of adding new areas to the National Wilderness Preservation System generally seek designations of specific areas to preserve them in their current condition and to prevent development activities from altering their wilderness character. Most areas protected as or proposed for wilderness are undeveloped, with few (if any) signs of human activity, such as roads and structures. The principal benefit of a wilderness designation is to maintain such undeveloped conditions and the values that such conditions generate—clean water, undisturbed wildlife habitats, natural scenic views, opportunities for nonmotorized recreation (e.g., backpacking), unaltered research baselines, and for some, the simple knowledge of the existence of such pristine places. Opponents of wilderness designations generally seek to retain development options for federal lands. The potential use of lands and resources can provide economic opportunities through extracting and developing the resources, especially in the relatively rural communities in and around the federal lands. The principal cost of a wilderness designation is the lost opportunity (opportunity costs) for economic activity resulting from resource extraction and development. While some economic activities—such as grazing and some recreation—are allowed to continue within wilderness areas, many are prohibited. The potential losses for some resources—such as timber harvesting—can often be determined with relative accuracy, since the quality and quantity of the resource can be measured. However, for other resources—particularly minerals—the assessments of the quality and quantity of the unavailable resources are more difficult to determine, and thus the opportunity costs are less certain. The potential benefits and opportunity costs of wilderness designation can rarely be fully quantified and valued. Thus, decisions about wilderness generally cannot be based solely on a clear cost-benefit or other economic analysis. Rather, deliberations commonly focus on trying to maximize the benefits of preserving pristine areas and minimize the resulting opportunity costs. However, individuals and groups who benefit from wilderness designations may differ from those who may be harmed by lost opportunities, increasing conflict and making compromise difficult. In general, Congress addresses several issues when drafting and considering wilderness bills. These issues include the general pros and cons of wilderness designation—generally and regarding identified areas of interest—and specific provisions regarding management of wilderness areas to allow or prohibit certain uses. The first step in developing legislation to designate wilderness areas is to identify which areas to designate. The Wilderness Act specified that wilderness areas are "at least 5,000 acres of land or … of sufficient size to make practicable its preservation and use in an unimpaired condition"; but no minimum size is required for designations made under new legislation. As a result, wilderness areas have taken all shapes and sizes; the smallest is the Pelican Island Wilderness in Florida, with only 5½ acres, and the largest is the Mollie Beattie Wilderness (Arctic National Wildlife Refuge) in Alaska, with 8.0 million acres. Many wilderness statutes have designated a single area, or even a single addition to an existing area.