The first known account of Park City appeared in the journal of Captain William Clark of the Lewis and Clark Expedition. He and his men journeyed down the Yellowstone River, after they split with Captain Lewis' party. Clarks' party took a route that put them on the Yellowstone and they explored the valley to where it flows into the Missouri. The notes of the party read that they spent a week in the valley where Youngs Point is located and hewed boats from the giant cottonwood trees which grew along the river.