Old Faithful is one of the most-visited features of Yellowstone National Park. John Colter is credited with being the first non-indigenous person to visit the area in 1807. In 1870 a government-sponsored expedition was mounted to study the area; two years later, Yellowstone was established as the first national park. Old Faithful sends a geyser of hot water and steam to a height of about 165 feet (50 m) for 2-5 minutes at intervals between 30 and 90 minutes. This phenomenon has been observed for more than 100 years. Yellowstone covers 3,468 square miles (8,983 square km) in eastern Idaho, southern Montana, and northwestern Wyoming. Most of the park is on a plateau between 7,000-8,000 feet. Fires in 1988 affected about one-fifth of the area of the park and destroyed about 10 percent of the trees.