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The United States has 59 protected areas known as national parks that are operated by the National Park Service, an agency of the Department of the Interior. National parks must be established by an act of the United States Congress. The first national park, Yellowstone, was signed into law by President Ulysses S. Grant in 1872, followed by Mackinac National Park in 1875 (decommissioned in 1895), and then Rock Creek Park (later merged into National Capital Parks), Sequoia and Yosemite in 1890. The Organic Act of 1916 created the National Park Service “to conserve the scenery and the natural and historic objects and wildlife therein, and to provide for the enjoyment of the same in such manner and by such means as will leave them unimpaired for the enjoyment of future generations.” Many current National Parks had been previously protected as National Monuments by the President under the Antiquities Act before being upgraded by Congress. Seven national parks (six in Alaska) are paired with a National Preserve. While administered together, they are considered as separate units and their areas are not included in the figures below. The newest national park is Pinnacles National Park, upgraded in 2013.
Criteria for the selection of National Parks include natural beauty, unique geological features, unusual ecosystems, and recreational opportunities (though these criteria are not always considered together). National Monuments, on the other hand, are frequently chosen for their historical or archaeological significance.
Twenty-seven states have national parks, as do the territories of American Samoa and the United States Virgin Islands. California has the most (nine), followed by Alaska (eight), Utah (five), and Colorado (four). The largest national park is Wrangell–St. Elias in Alaska: at over 8 million acres (32,000 km2), it is larger than each of the nine smallest states. The next three largest parks are also in Alaska. The smallest park is Hot Springs, Arkansas, at less than 6 thousand acres (24 km2). The total area protected by national parks is approximately 51.9 million acres (210,000 km2), for an average of 895 thousand acres (3,620 km2) but a median of only 317 thousand acres (1,280 km2). The most-visited national park is Great Smoky Mountains in North Carolina and Tennessee, with over ten million visitors in 2014, followed by Arizona’s Grand Canyon, with over 4.7 million. In contrast, only 12,669 people visited the remote Gates of the Arctic in Alaska in the same year. Fourteen national parks are designated World Heritage Sites.
A few former national parks are no longer designated as such, or have been disbanded. Other units of the National Park Service are sometimes incorrectly referred to as national parks; they are listed here.
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