Setting the Stage:
A General Overview
Jefferson's Dream
In 1803, under President Thomas Jefferson, the United States negotiated the Louisiana Purchase with France. The $15 million deal gave the United States 828,000 square miles and more than doubled the country's size. What the new territory held was largely a mystery, however. Months before the actual purchase, Jefferson commissioned the Lewis & Clark Expedition to help solve the mystery. He prepared a long list of objectives and instructions for the explorers.
In addition to gaining scientific knowledge about the West, Jefferson hoped the military expedition would find a water route to the Pacific Ocean. He also wanted detailed information about Native peoples who lived in the territory. He appointed Meriwether Lewis, his personal secretary, to lead the expedition. To prepare, Lewis took intensive training in medicine and other disciplines, including geography, botany, geology and astronomy, under some of the nation's leading scientists. Lewis chose William Clark, once his superior officer, to be co-commander. The two met on October 14, 1803 at Clarksville in Indiana Territory to make final preparations for the journey.
The Beginning of the Journey
With nine recruits and Clark's slave, York, the captains set out from Falls of the Ohio near Louisville, Kentucky, on October 26, 1803. They spent the winter of 1803-1804 at Camp Dubois at the mouth of the Wood River, just across the Mississippi River from St. Louis, Mo. With added recruits, the explorers known as the Corps of Discovery set out on May 14, 1804 and traveled up the Missouri River. Near present-day Sioux City, Iowa,
Sergeant Charles Floyd died. His death was likely caused by a ruptured appendix, although we will never know for sure.
The explorers continued up the Missouri and set up their 1804-05 winter camp at the Mandan and Hidatsa villages, north of present-day Bismarck, N.D. There they encountered Sacagawea, a young Shoshone woman who was married to French-Canadian fur trader Toussaint Charbonneau. The captains hired Charbonneau as an interpreter. Sacagawea, with their newborn son Jean Baptiste, would accompany the explorers and provide valuable communication skills. She and her baby would also symbolize the expedition's peaceful intentions to Native peoples encountered along the way.
Reaching the Pacific
The Corps of Discovery left Fort Mandan on April 7, 1805, sending a return party downstream on the keelboat with specimens and reports for Jefferson. The permanent party resumed the westward journey, crossing the Rocky Mountains and continuing on to the Columbia River. The explorers reached the Pacific Ocean in November 1805 and set up their third winter camp, Fort Clatsop, on the south side of the mouth of the Columbia River.
Returning Home
On September 23, 1806, the expedition returned to St. Louis with documentation of plants, animals and other natural resources new to Western science. They had met in council with chiefs of more than 50 Native tribes. They had recorded discoveries and observations that would lead to the production of critical maps of the West. They had traveled almost 8,000 miles to the Pacific Coast and back. They had determined that there was no direct water route to the Pacific Ocean.
Source: http://www.fs.fed.us/r1/lewisclark/lcic/index.html