Grand Teton National Park is an American national park in northwestern Wyoming. At approximately 310,000 acres, the park includes the major peaks of the 40-mile-long Teton Range as well as most of the northern sections of the valley known as Jackson Hole. Grand Teton National Park is only 10 miles south of Yellowstone National Park. Along with surrounding national forests, these three protected areas constitute the almost 18-million-acre Greater Yellowstone Ecosystem, one of the world's largest intact mid-latitude temperate ecosystems. Efforts to preserve the region as a national park began in the late 19th century, and was established as a national park on February 26, 1929.