Lewis and Clark Expedition
Departure

The Corps of Discovery departed from Camp Dubois (Camp Wood) at 4 pm on May 14, 1804. Under Clark's command, they traveled up the Missouri River in their keelboat and two pirogues to St. Charles, Missouri where Lewis joined them six days later. The expedition set out the next afternoon, May 21. While accounts vary, it is believed the Corps had as many as 45 members, including the officers, enlisted military personnel, civilian volunteers, and York, an African-American man enslaved by Clark.

From St. Charles, the expedition followed the Missouri through what is now Kansas City, Missouri, and Omaha, Nebraska. On August 20, 1804, Sergeant Charles Floyd died, apparently from acute appendicitis. He had been among the first to sign up with the Corps of Discovery and was the only member to die during the expedition. He was buried at a bluff by the river, now named after him, in what is now Sioux City, Iowa. His burial site was marked with a cedar post on which was inscribed his name and day of death. 1 mile (2 km) up the river, the expedition camped at a small river which they named Floyd's River. During the final week of August, Lewis and Clark reached the edge of the Great Plains, a place abounding with elk, deer, bison, pronghorn and beavers.

The Lewis and Clark Expedition established relations with two dozen Native American nations, without whose help the group would have risked starvation during the harsh winters and/or become hopelessly lost in the vast ranges of the Rocky Mountains.

The Americans and the Lakota nation (whom the Americans called Sioux or "Teton-wan Sioux") had problems when they met, and there was a concern the two sides might clash. According to Harry W. Fritz, "All earlier Missouri River travelers had warned of this powerful and aggressive tribe, determined to block free trade on the river.... The Sioux were also expecting a retaliatory raid from the Omaha tribe, to the south. A recent Sioux raid had killed 75 Omaha men, burned 40 lodges, and taken four dozen prisoners." The expedition held talks with the Lakota near the confluence of the Missouri and Bad Rivers in what is now Fort Pierre, South Dakota.

One of their horses disappeared, and they believed the Sioux were responsible. Afterward, the two sides met and there was a disagreement, and the Sioux asked the men to stay or to give more gifts (or tribute) instead, before being allowed to pass through their territory. Clark wrote they were "warlike" and were the "vilest miscreants of the savage race". They came close to blows several times, until the Lakota chief, Black Buffalo, persuaded Lewis to distribute more tobacco to the assembled warriors. Lewis complied and the expedition was allowed to continue upstream to the Arikara villages.

In the winter of 1804 – 05, the party built Fort Mandan, near present-day Washburn, North Dakota. Just before departing on April 7, 1805, the expedition sent the keelboat back to St. Louis with a sample of specimens, some never-before-seen east of the Mississippi. One chief asked Lewis and Clark to provide a boat for passage through their national territory. The Americans quickly continued westward (upriver), and camped for the winter in the Mandan nation's territory.

After the expedition had set-up camp, nearby tribal members came to visit in fair numbers, some staying all night. For several days, Lewis and Clark met in council with Mandan chiefs. Here they met a French-Canadian fur trapper named Toussaint Charbonneau, and his young Shoshone wife, Sacagawea. Charbonneau, at this time, began to serve as the expedition's translator. Peace was established between the expedition and the Mandan chiefs with the sharing of a Mandan ceremonial pipe. By April 25, Captain Lewis wrote his progress report of the expedition's activities and observations of the Native American nations they had encountered to-date in A Statistical view of the Indian nations inhabiting the Territory of Louisiana, which outlined the names of various tribes, their locations, trading practices and water routes used, among other points. President Jefferson would later present this report to Congress.

They followed the Missouri to its headwaters, and over the Continental Divide at Lemhi Pass, then north to Traveler's Rest, and crossed the Bitteroots at Lolo Pass. They descended on foot, then proceeded in canoes down the Clearwater, Snake, and Columbia rivers, past Celilo Falls and present-day Portland, at the confluence of the Willamette and Columbia rivers. Lewis and Clark used William Robert Broughton 's 1792 notes and maps to orient themselves once they reached the lower Columbia River. The sighting of Mount Hood and other stratovolcanos confirmed that the expedition had almost reached the Pacific Ocean.
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