Who was the trapper and explorer who was part of the Lewis and Clark expedition John?

The trapper and explorer you are referring to is John Colter. He was a member of the Lewis and Clark Expedition from 1804 to 1806 and is known for his extensive knowledge of the western territories. After the expedition, Colter became one of the first American explorers to venture into the Yellowstone area, where he encountered its geothermal features. His explorations contributed significantly to the understanding of the American West.