While Lewis and three other members of the Corps of Discovery were headed to Beaverhead Rock overland, Clark and the rest of the explorers headed there by river. On August 13, 1805, Clark ascended a rocky limestone outcropping, now known as Clark's Lookout, where he viewed the region through a telescope, made a number of compass readings and sketched a map of the area. Five days earlier on August 8, 1805, Sacagawea had identified Beaverhead Rock, the point of a high plain, as the place where her people, the Shoshones, had been when she was kidnapped. Lewis, understanding the importance of finding the Shoshone Indians and obtaining horses and aid from them before winter, went ahead with a small party. Clark and the remainder of the group continued up the river. After days of difficult navigation, Clark and his companions stumbled upon the limestone outcropping and a nearby stream named McNeal's Creek (now Blacktail Deer Creek) after Hugh McNeal, a member of the party.

That night, after travelling 16 miles by water and five miles by land, the explorers camped a few miles southwest of present-day Dillon, Montana. From here they traveled upriver, crossed the Continental Divide and rejoined Lewis on the banks of the Lemhi River. The explorers soon received critical aid from the Shoshone Indians, led by Sacagawea's brother Chief Cameahwait, to continue their journey.

Clark's Lookout is located one mile north of Dillon, Montana on Old State Hwy. 91. Clark's Lookout State Park is open to the public year-round, free of charge. Call 406-834-3413, or visit the park's website for further information.