Missouri Headwaters State Park, Three Forks

Missouri Headwaters State Park is a Montana state park that marks the official start of the Missouri River. It includes the Three Forks of the Missouri National Historic Landmark, designated in 1960 because the site is one where the Lewis and Clark Expedition camped in 1805. The park is open for day use and camping, offering hiking trails, hunting, and water-related activities. It is located on Trident Road northeast of Three Forks, Montana at an elevation of 4045ft.
The bulk of Missouri Headwaters State Park is found on a peninsula flanked on the east by the Gallatin River and the west by the Missouri River and the Madison River. Small parts of the park are also located on the east bank of the Gallatin River, and an island in the Missouri just below the confluence of the Madison and Jefferson Rivers. The total park size is 532acre. The Jefferson River meets the Madison and Missouri roughly midway through the park's north-south extent.
The Lewis and Clark Expedition encamped at the confluence site on July 26, 1805. On July 28, Meriwether Lewis wrote in his journal:
Both Capt. C. and myself corresponded in opinon with rispect(sic) to the impropriety of calling either of these streams the Missouri and accordingly agreed to name them after the President of the United States and the Secretaries of the Treasury and State. The expedition were likely the first white men to ever penetrate this landscape. Lewis and Clark were at first uncertain how to proceed, and scouted each of the branches before ultimately departing on July 30 up the Jefferson River. The expedition also passed the forks on its return journey on July 13, 1806.