The history of Yellowstone National Park has two beginnings. It became an official national park, and the US' first national park in 1872. It was nearly 70 years before that though, in 1806, that Yellowstone began its path to becoming a national park.
John Colter is credited with "discovering" Yellowstone National Park. Colter was one of the members of the Lewis and Clark Expedition before deciding to leave and join a group of fur trappers. Throughout his travels he visited what is thought to be present day Tower Fall, experiencing hot springs and geysers. Upon rejoining civilization, he described what he saw as a place of "fire and brimstone" but was dismissed as crazy. His claims seemed to be verified when trappers and other mountain men described similar scenes over the next forty years. Even Jim Bridger, a well-known explorer, was dismissed when describing boiling springs and spouting water as he had a reputation for stretching the facts.
It wasn't until 1869 when an official report was filed describing the Cook-Folsom-Peterson Expedition which explored an area from Yellowstone River to Yellowstone Lake. The next year another expedition, including the surveyor-general of Montana, spent a month exploring the area and collecting specimens. Members of these groups were so impressed with what they saw that they pushed to have the area made into a protected wildlife area to be known as the Great Geyser Basin.
F.V. Hayden, who had the misfortune of a failed attempted to explore the region a decade earlier, was able to successfully reverse his fortunes in 1871. He obtained government sponsorship and brought with him a much larger entourage than he had on his previous attempt. His exploration, dubbed the Hayden Geological Survey of 1871, returned with large-format photographs and paintings. Upon return, Hayden created a detailed report, including those photographs and paintings. This report helped convince President Ulysses S. Grant to sign into law the creation of Yellowstone National Park on March 1, 1872.
Today Yellowstone National Park, spanning 3,468 acres, is one of the most visited places in the US. The world famous Old Faithful Geyser is the most well-known attraction of Yellowstone National Park, while many others come for its abundant and varied wildlife and host of awe-inspiring geysers and hot springs.