Three Forks of the Missouri - Missouri Headwaters State Park, MT. On July 28, 1805, at the confluence of the Gallatin, Madison and Jefferson rivers, Lewis correctly chose the Jefferson as the headwaters of the Missouri. Sacagawea recognized this as the site where she had been abducted by the Hidatsa five years earlier. With winter approaching, they had to find the Shoshone and get the horses needed for the portage.
