At the headwaters of the Missouri River, the Jefferson and Madison Rivers converge, and the Gallatin joins one mile downstream to form the Missouri. Here Lewis and Clark achieved a major goal of their expedition by exploring the Missouri to its source. Clark arrived first on July 25, 1805, explored the area, and continued on in hopes of finding the Shoshone and the horses the party desperately needed, then returned two days later exhausted and ill. Lewis arrived that same day, and the whole party camped for three days while continuing to explore the area. The camp is thought to have been less than a mile up the Jefferson River on private land. As they left the headwaters, they were anxious to find the Shoshones for horses to continue across the mountains, and on August 13, 1805, the Corps met the Lemhi Shoshone, including Sacagawea’s brother. On the return trip, Lewis and Clark split up to explore more territory north and south of the Missouri River, and Clark passed through here again in the summer of 1806. Lewis recorded that he and Clark agreed it was improper to call any of the three streams the Missouri and named them the Jefferson, Madison, and Gallatin after President Jefferson, Secretary of State James Madison, and Secretary of the Treasury Albert Gallatin. Clark, the expedition’s mapmaker, was ill during his stay here with fever and flulike symptoms.