Missouri Headwaters State Park

Missouri Headwaters State Park covers about 535 acres at the official start of the Missouri River, northeast of Three Forks, Montana, at an elevation of 4,045 feet. Most of it lies on a peninsula with the Gallatin River on the east and the Missouri and Madison rivers on the west, and the Jefferson River joins the Madison and Missouri roughly midway through the park.

The park offers camping, hiking trails, hunting and water-related activities. It includes the Three Forks of the Missouri National Historic Landmark, designated in 1960 because the Lewis and Clark Expedition camped here in 1805.

The expedition camped at the confluence on July 26, 1805. Meriwether Lewis wrote that he and William Clark agreed it would be improper to call any of the three streams the Missouri, so they named them after the President and the Secretaries of the Treasury and State. After scouting each branch, they left on July 30 and went up the Jefferson. They passed the forks again on their return on July 13, 1806. In the 19th century, fur trappers often used the area as a campsite, and preservation groups began acquiring land for the park in the 1960s.

Their decision not to call the Jefferson the Missouri still fuels a debate about the longest river in North America. The Missouri and Mississippi are nearly identical in length, and re-channeling for hydroelectric plants trimmed 72 miles from the Missouri, so it is now sometimes ranked second. If the Jefferson were counted as part of the Missouri, experts at the U.S. Geological Survey would still technically consider the Missouri the longest river. The farthest headwater point is also disputed, with two claimed sites that drain into the Jefferson: Trail Creek above Lemhi Pass, at around 8,600 feet, and Brower’s Spring in the Centennial Mountains, at around 8,800 feet.