Jefferson River - Lewis and Clark Expedition

Lewis and Clark Expedition

Little was known about the American West at the beginning of the nineteenth century. The Missouri River flowed southeast from an unknown source, joining the Mississippi River before flowing south to the Gulf of Mexico. The Columbia River originated at a similar latitude as the Missouri, and flowed west to the Pacific Ocean. What lay in between was the subject of much speculation.

The United States acquired the Missouri River watershed through the Louisiana Purchase of 1803, and President Thomas Jefferson sent Meriwether Lewis and William Clark with a company of men to explore up the Missouri in the hopes of finding a navigable water route to the Pacific, with a low portage connecting one watershed with the other. The Expedition departed from Saint Louis, Missouri in the spring of 1804, ascended the Missouri River that summer, then wintered over with the Hidatsa Indians in North Dakota, where they met Toussaint Charbonneau and his Shoshone wife Sacagawea. Lewis and Clark hired Charbonneau to join the expedition, in part because Sacagawea's people were native to the Missouri headwaters. The Lewis and Clark Expedition arrived at the Missouri Headwaters on 27 July 1805.

Of the three streams that make up the headwaters of the Missouri, the eastern fork is the smallest, while the larger middle and western forks are of relatively equal size. Therefore, Lewis and Clark concluded that it would be inappropriate for any fork to retain the name "Missouri." Instead, they named the western fork the Jefferson, the middle fork as the Madison, and the eastern fork as the Gallatin, as Meriwether Lewis noted in his journal on July 28th, 1805:

Both Capt. C. and myself corresponded in opinon with rispect 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 rested a couple days at the Missouri headwaters, then began to ascend the Jefferson River, using ropes to pull the dugout canoes upstream against the current. Along the way they hunted deer, elk, bighorn sheep, and encountered grizzly bears. Describing the upper Jefferson River, Lewis recorded on August 2, 1805:

The valley though which our rout of this lay and through which the river winds it's meandering course is a beatifull level plain with but little timber and that on the verge of the river. the land is tolerably fertile, consisting of a black or dark yellow loam, and covered with grass from 9 Inches to 2 feet high. The plain ascends gradually on either side of the river to the bases of two ranges of mountains which ly parallel to the river and which terminate 〈it's〉 the width of the vally. the tops of these mountains were yet partially covered with snow while we in the valley. were suffocated nearly with the intense heat of the midday sun. the nights are so could that two blankets are not more than sufficient covering.

Arriving at a major confluence, Lewis and Clark named the western fork the Wisdom River, the eastern fork the Philanthropy River and retained the middle fork as a continuation of the Jefferson River. However, none of these names were retained. These rivers are known today as the Big Hole, the Ruby, and the Beaverhead.

The Jefferson River is a segment of the Lewis and Clark National Historic Trail, established by Congress in 1978 and administered by the National Park Service.