At Three Forks, the Jefferson, Madison, and Gallatin rivers converge to form the headwaters of the Missouri River, a place where Native peoples prospered more than 10,000 years ago and where a long-traveled corridor later served explorers, fur trappers, miners, farmers, and homesteaders. In July 1805, Lewis and Clark traveled through this valley, recorded places such as Crimson Bluffs, Yorks Islands, and the Second Gates of the Rocky Mountains, and Sacajawea recognized the area where she had been captured from her people by a Hidatsa raiding party; on July 28, 1805, the three rivers were named for Thomas Jefferson, James Madison, and Albert Gallatin, and Clark returned to the headwaters in August 1806. The region later developed an economy based on agriculture, cattle, minerals, timber, and cement, while Three Forks was founded by the Chicago, Milwaukee & St. Paul Railroad in 1908 and the railroad era ended in 1980. The Missouri River remained central to the valley’s life, and major changes came with the 1896 construction of a dam and power plant above the site of Canyon Ferry, the creation of Lake Sewell, and the later study begun in 1941 that led to the completion of the new Canyon Ferry Dam in 1954, expanding irrigation and adding recreation and wildlife benefits.