Mississippi in terms of length. If the Jefferson were included in the Missouri length, it would technically still be considered the longest river by experts of the United States Geological Survey. The utmost headwaters of the Missouri are subject to debate but two commonly claimed locations ultimately drain into the Jefferson. Lewis on August 12, 1805 said he visited the headwaters on Trail Creek just above Lemhi Pass on the Continental Divide in the Beaverhead Mountains at around 8,600 feet which he described: the most distant fountain of the waters of the mighty Missouri in surch(sic) of which we have spent so many toilsome days and wristless(sic) nights. In 1888 Jacob V. Brower, who had championed turning the headwaters of the Mississippi River into a Minnesota state park, visited another site which today is also claimed to be the furthest point on the Missouri. Brower published his finding in 1896 in "The Missouri: Its Utmost Source." Brower's Spring, as the site is now known, is at around 8,800 feet in the Centennial Mountains. The site is commemorated by a rock pile at the source of Hellroaring Creek which flows into Red Rock River and then into Clark Canyon Reservoir where it joins the Beaverhead then the Big Hole River before ultimately hooking up with the Jefferson. See also List of National Historic Landmarks in Montana National Register of Historic Places listings in Gallatin County, Montana References External links Missouri Headwaters State Park Montana Fish, Wildlife & Parks Missouri Headwaters State Park Map Montana Fish, Wildlife & Parks State parks of Montana Provincial and state parks in the Rocky Mountains Missouri River Protected areas of Gallatin County, Montana Protected areas established in 1947 1947 establishments in Montana Lewis and Clark Expedition History of the Rocky Mountains National Historic Landmarks in Montana National Register of Historic Places in Gallatin County, Montana