The United States has 58 protected areas known as national parks, which 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 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.”
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