The International Union for Conservation of Nature has put forth a set of characteristics that make up a “national park”. There are more than six thousand national parks in the world that meet this set of criteria, with the United States national parks meeting all of them. Generally a national park is a large area with one or more ecosystems that have not been materially modified by humans and where visitors are allowed to enter with the purpose of enjoying for recreation, education, or for cultural reasons.
President Teddy Roosevelt established the first official United States national park in 1872 with Yellowstone National Park. It was not until President Woodrow Wilson was in office when the National Park Service was established to take control of the national parks, monuments, and historic sites, and battlefields.