While Lewis and three others traveled overland to Beaverhead Rock, Clark and the rest of the Corps headed there by river. On August 13, 1805, Clark ascended a limestone outcropping, now known as Clark's Lookout. He viewed the region through a telescope, made a number of compass readings, and sketched a map of the area.
After travelling 16 miles by water and five miles by land, the Corps spent the night few miles southwest of present-day Dillon, Montana. From here they traveled upriver, crossed the Continental Divide and joined Lewis on the banks of the Lemhi River. They met with the Shoshone, led by Sacagawea's brother Chief Cameahwait, and received aid critical to their continuing the journey west.