The protected areas of the United States are managed by an array of different federal, state, tribal and local level authorities and receive widely varying levels of protection. Some areas are managed as wilderness, while others are operated with acceptable commercial exploitation. As of 2015, the 25,800 protected areas covered 1,294,476 km2 (499,800 sq mi), or 14 percent of the land area of the United States. This is also one-tenth of the protected land area of the world. The U.S. also had a total of 787 National Marine Protected Areas, covering an additional 1,271,408 km2 (490,893 sq mi), or 12 percent of the total marine area of the United States.
Some areas are managed in concert between levels of government. The Father Marquette National Memorial is an example of a federal park operated by a state park system, while Kal-Haven Trail is an example of a state park operated by county-level government.
As of 2007, according to the United Nations Environment Programme, the U.S. had a total of 6,770 terrestrial nationally designated (federal) protected areas. Federal level protected areas are managed by a variety of agencies, most of which are a part of the National Park Service, a bureau of the United States Department of the Interior. They are often considered the crown jewels of the protected areas. Other areas are managed by the United States Forest Service, the Bureau of Land Management and the United States Fish and Wildlife Service. The United States Army Corps of Engineers is claimed to provide 30 percent of the recreational opportunities on federal lands, mainly through lakes and waterways that they manage.
The highest levels of protection, as described by the International Union for Conservation of Nature (IUCN), are Level I (Strict Nature Reserves & Wilderness Areas) and Level II (National Parks). The United States maintains 12 percent of the Level I and II lands in the world. These lands had a total area of 210,000 sq mi (540,000 km2).
A confusing system for naming protected areas results in some types being used by more than one agency. For instance, both the National Park Service and the U.S. Forest Service operate areas designated National Preserves and National Recreation Areas. The National Park Service, the U.S. Forest Service, and the Bureau of Land Management operate areas called National Monuments. National Wilderness Areas are designated within other protected areas, managed by various agencies and sometimes wilderness areas span areas managed by multiple agencies.
There are existing federal designations of historic or landmark status that may support preservation via tax incentives, but that do not necessarily convey any protection, including a listing on the National Register of Historic Places or a designation as a National Historic Landmark. States and local zoning bodies may or may not choose to protect these. The state of Colorado, for example, is very clear that it does not set any limits on owners of NRHP properties.
Federal protected area designations
International protected area designations
Every state has a system of state parks. State parks vary widely from urban parks to very large parks that are on a par with national parks. Some state parks, like Adirondack Park, are similar to the National parks of England and Wales, with numerous towns inside the borders of the park. About half the area of the park, some 3,000,000 acres (1,200,000 ha), is state-owned and preserved as "forever wild" by the Forest Preserve of New York. Wood-Tikchik State Park in Alaska is the largest state park by the amount of contiguous protected land; it is larger than many U.S. National Parks, with some 1,600,000 acres (650,000 ha), making it larger than the state of Delaware. Many states also operate game and recreation areas.
Various counties, cities, metropolitan authorities, regional parks, townships, soil conservation districts and other units manage a variety of local level parks. Some of these are little more than picnic areas or playgrounds; however, others are extensive nature reserves. South Mountain Park in Phoenix, Arizona, for example, is called the largest city park in the United States; it spans 25 sq mi (65 km2) and contains 58 mi (93 km) of trails.