Grand Canyon National Park, located in northwestern Arizona, is the 15th site in the United States to have been named as a national park. The park's central feature is the Grand Canyon, a gorge of the Colorado River, which is often considered one of the Wonders of the World. The park, which covers of unincorporated area in Coconino and Mohave counties, received more than six million recreational visitors in 2017, which is the second highest count of all American national parks after Great Smoky Mountains National Park. The Grand Canyon was designated a World Heritage Site by UNESCO in 1979. The park celebrated its 100th anniversary on February 26, 2019. History The Grand Canyon became well known to Americans in the 1880s after railroads were built and pioneers developed infrastructure and early tourism. In 1903, President Theodore Roosevelt visited the site and said, The Grand Canyon fills me with awe. It is beyond comparison—beyond description; absolutely unparalleled through-out the wide world ... Let this great wonder of nature remain as it now is. Do nothing to mar its grandeur, sublimity and loveliness. You cannot improve on it. But you can keep it for your children, your children's children, and all who come after you, as the one great sight which every American should see. Despite Roosevelt's enthusiasm and strong interest in preserving land for public use, the Grand Canyon was not immediately designated as a national park. The first bill to establish Grand Canyon National Park was introduced in 1882 by then-Senator Benjamin Harrison, which would have established Grand Canyon as the third national park in the United States, after Yellowstone and Mackinac. Harrison unsuccessfully reintroduced his bill in 1883 and 1886; after his election to the presidency, he established the Grand Canyon Forest Reserve in 1893. Theodore Roosevelt created the Grand Canyon Game Preserve by proclamation on November 28, 1906, and the Grand Canyon National Monument on January 11, 1908. Further Senate bills to establish the site as a national park were introduced and defeated in 1910 and 1911, before the Grand Canyon National Park Act was finally signed by President Woodrow Wilson on February 26, 1919. The National Park Service, established in 1916, assumed administration of the park. The creation of the park was an early success of the conservation movement. Its national park status may have helped thwart proposals to dam the Colorado River within its boundaries.