Corps of Discovery

Jefferson's Instructions
These were the final instructions given to Meriwether Lewis and William Clark before they embarked upon their journey into the Louisiana Purchase. The beauty they discovered was beyond their wildest expectations. The people they encountered represented dozens of unique cultures, and enabled the successful completion of their mission. The geography, flora, fauna and other natural phenomena they documented resulted in an enormous body of scientific information that was new to the western world. The indigenous Native Americans were already very familiar with these "discoveries." Even though an easy water route across the continent was not found, these accomplishments make the Lewis and Clark Expedition one of the most successful explorations of all time.

Jefferson's final instructions to Lewis reflect the broad range of the President's interests. The expedition was meant to prepare the way for the extension of the American fur trade and to advance geographical knowledge. Jefferson provided the best supplies, clothing, firearms, equipment and rations then available. Lewis and Clark were instructed to observe and record the entire range of natural history and ethnology of the areas they explored, and note possible resources which would support future settlement. The Louisiana Purchase of 1803 had doubled the size of the nation, but a good share of the territory the expedition would explore was unmapped. Jefferson envisioned the nation's eventual expansion to the Pacific, and wanted to strengthen the American claim to the northwest Columbia Basin.

The Expedition Begins
In December 1803 William Clark established "Camp River Dubois" at the confluence of the Mississippi and Missouri Rivers, north of St. Louis. While there he recruited and trained men, while Lewis spent time in St. Louis, conferring with traders about the Upper Missouri regions and obtaining maps made by earlier explorers. On May 14, 1804 William Clark and the Corps of Discovery left Camp River Dubois, and were joined by Meriwether Lewis in St. Charles, Missouri. The party numbered over 45, and included 27 young, unmarried soldiers, a French-Indian interpreter, and Clark's Black slave York. An additional group of men, engagés, would travel only to the Mandan country for the first winter, and these included six soldiers and several French boatmen.

Travel up the Missouri River was difficult and exhausting due to heat, injuries, insects, and the troublesome river itself, with its strong current and many snags. The expedition used a specially built keelboat and two smaller boats, called pirogues, to carry their supplies and equipment, averaging 15 miles per day. During this phase of the journey the group suffered the only casualty of the expedition, Sgt. Charles Floyd. Buried near modern-day Sioux City, Iowa, it is believed that Floyd died of a burst appendix. Relations with Native Americans were generally good, and councils were held with the Otos and Missouris. The explorers gave peace medals to the most important chiefs of each tribe. By October the Corps of Discovery reached the Mandan and Hidatsa villages, where they built "Fort Mandan" (near present-day Washburn, North Dakota), and spent the winter of 1804-1805.

During the winter Lewis and Clark made copious notes in their journals, drew maps, and learned of the geography that lay ahead from American Indians in the area of the camp. They recruited an interpreter named Toussaint Charbonneau, who brought along his Shoshoni Indian wife, Sacagawea, and her newborn baby boy, Jean Baptiste.

Westward To The Pacific
On April 7, 1805 Lewis and Clark sent the keelboat back to St. Louis with an extensive collection of zoological, botanical, and ethnological specimens as well as letters, reports, dispatches, and maps, and resumed their westward journey in two pirogues and six dugout canoes. The Corps of Discovery, now numbering 33, traveled into regions which had been explored and seen only by Native Americans. After crossing most of modern-day Montana the explorers were held up for over a month by the extensive waterfalls at Great Falls. Lewis tried to use a special collapsible boat he had manufactured at Harpers Ferry, but the animal skins could not be sealed over the boat's iron frame and it had to be abandoned. By August 17 they reached the navigable limits of the Missouri River near the Rocky Mountains, and turned south up the Jefferson River. The expedition crossed the Continental Divide through Lemhi Pass, and purchased horses from the Shoshonis, Sacagawea's people. They traveled north to Lolo Pass where they crossed the Bitteroot Range on the Lolo Trail; this was the most difficult part of the journey. Nearly starved, Lewis and Clark reached the country of the Nez Perce on the Clearwater River in Idaho, and left their horses for dugout canoes. From there they floated down the Clearwater, Snake, and Columbia rivers, reaching the Pacific Ocean by November of 1805.

In December the explorers built Fort Clatsop on the south side of the Columbia River (near present-day Astoria, Oregon), and settled in for the winter. Lewis and Clark accomplished considerable scientific work while on the Pacific coast, gathering and recording information regarding the country and its inhabitants, despite constant rain and plaguing insects. A detail of men was assigned to make salt by boiling sea water.

The Return Journey
On March 23, 1806 the return trip began. After a tough journey up the Columbia against strong currents, the party retrieved their horses from the Nez Perce, and waited for the deep mountain snow to melt. After crossing the Bitteroots the party split at the Lolo Pass to add to the geographical knowledge they would gather. Confident of their survival, Lewis went north while Clark went south. While on the Marias River Lewis' party had a fight with a party of Blackfeet Indians, and were forced to kill two of them. This was the only violent incident of the entire journey. The Corps of Discovery was reunited in North Dakota, at the mouth of the Yellowstone River. They left Charbonneau, Sacagawea and the baby at the Mandan villages, continued down the Missouri River, and arrived in St. Louis on September 23, 1806.

The Importance Of The Expedition
The results and accomplishments of the Lewis and Clark expedition were extensive. It altered the imperial struggle for the control of North America, particularity in the Pacific northwest, by strengthening the U.S. claim to the areas now including the states of Oregon and Washington. Lewis and Clark achieved an impressive record of peaceful cooperation with the Indians and generated American interest in the fur trade. This had a far reaching effect, since it led to further exploration and commercial exploitation of the West. Lewis and Clark added to geographic knowledge by determining the true course of the Upper Missouri and its major tributaries, and producing important maps of these areas. They forever destroyed the dream of a Northwest Passage, but proved the success of overland travel to the Pacific. The expedition compiled the first general survey of life and material culture of the Native American tribes they encountered.

Lewis and Clark made significant additions to the zoological and botanical knowledge of the continent, providing the first scientific descriptions of many new species of animals, including the grizzly bear, prairie dog, pronghorn antelope, and mountain goat. They made the first attempt at a systematic record of the meteorology of the West, and less successfully attempted to determine the latitude and longitude of significant geographical points.

Lewis and Clark traveled over 8,000 miles in less than 2 1/2 years, losing only one member of their party, at a total cost to the taxpayer of $40,000. By any measure of scientific exploration, the Lewis and Clark expedition was phenomenally successful in terms of accomplishing its stated goals, expanding human knowledge, and spurring further curiosity and wonder about the vast American West.

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    Last updated: May 7, 2021

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