Take the Barretts exit off I-15, 8 miles south of Dillon, and you'll come face to face with Lewis's infamous Rattlesnake Cliffs, top left. As he sat under those cliffs on August 10th, 1805, waiting for Drouillard to hunt for lunch, literally, he saw a great number of rattlesnakes. Across I-15, at Barretts Dam, you'll be in the vicinity of William Clark's August 14th campsite. Above and right, the Beaverhead River, flowing north toward Barretts Dam. Top right, flowing from the south.