John Colter has quite a story in Wikipedia. Here's just part:

John Colter (c.1770–1775 – May 7, 1812 or November 22, 1813) was a member of the Lewis and Clark Expedition (1804–1806). Though party to one of the more famous expeditions in history, Colter is best remembered for explorations he made during the winter of 1807–1808, when he became the first known person of European descent to enter the region which later became Yellowstone National Park and to see the Teton Mountain Range. Colter spent months alone in the wilderness and is widely considered to be the first known mountain man.

https://en.wikipedia.org/wiki/John_Colter