The three forks region of southwestern Montana, where the headwaters of the Missouri River form from the Jefferson, Madison and Gallatin rivers, was the axis around which the Lewis and Clark expedition revolved. It was here in August 1805 that the luckiest event of the expedition took place. Sacagawea, the quiet Shoshone teenager who had accompanied the party as an interpreter, was discovered to be the sister of a powerful chief, Cameahwait. Suspicious of the Americans at first, Cameahwait was so joyful at seeing Sacagawea five years after her kidnapping by Hidatsa raiders that he overcame all his doubts. Cameahwait would prove to be a good friend to the explorers, helping them find their way across the last and greatest barrier to the Pacific: the Rocky Mountains.