On July 25, 1805, Clark was ahead of Lewis, scouting for signs of Sacagawea's Shoshone people, when he reached the place where three rivers come together to form the headwaters of the Missouri near today's Three Forks, Montana. When both captains studied the three forks, they agreed that this was the true beginning of the Missouri, but they did not want to give any single branch the old name "Missouri River." Instead, they chose to name the southwest fork the Jefferson River in honor of President Thomas Jefferson, the middle fork the Madison River for Secretary of State James Madison, and the southeast fork the Gallatin River for Treasury Secretary Albert Gallatin, then continued their journey up the Jefferson toward the mountains.