Yosemite National Park (/joʊˈsɛmɨti/ yoh-SEM-it-ee) is a United States National Park spanning eastern portions of Tuolumne, Mariposa and Madera counties in the central eastern portion of the U.S. state of California. The park, which is managed by the National Park Service, covers an area of 747,956 acres (1,168.681 sq mi; 302,687 ha; 3,026.87 km²) and reaches across the western slopes of the Sierra Nevada mountain chain. Over 3.7 million people visit Yosemite each year: most spend the majority of their time in the seven square miles (18 km²) of Yosemite Valley. Designated a World Heritage Site in 1984, Yosemite is internationally recognized for its spectacular granite cliffs, waterfalls, clear streams, giant sequoia groves, and biological diversity. Almost 95% of the park is designated wilderness. Yosemite was central to the development of the national park idea.