The reason i think they killed him.................was b/c he learned of the true reason Pres. Jefferson sent the expedition West..................recon on how to kill the Indians...............

The two-year exploration by Lewis and Clark was the first transcontinental expedition to the Pacific Coast by the United States; however, Lewis and Clark reached the Pacific 12 years after Sir Alexander Mackenzie had done so overland in Canada.^[9] They were accompanied by a fifteen-year-old Shoshone Indian woman, Sacagawea, the wife of a French-Canadian fur trader. The Corps of Discovery made contact with many Native Americans in the trans-Mississippi West and found them accustomed to dealing with European traders and already connected to global markets. After crossing the Rocky Mountains, the expedition reached the Oregon Country (which was disputed land beyond the Louisiana Purchase) and the Pacific Ocean in November 1805. They returned in 1806, bringing with them an immense amount of information about the region as well as numerous plant and animal specimens.^[14] They demonstrated the possibility of overland travel to the Pacific coast. The success of their journey helped to strengthen the American concept of "Manifest destiny" - the idea that the United States was destined to reach all the way across North America from Atlantic to Pacific.^[15][16]

Return and gubernatorial duties[edit]

After returning from the expedition, Lewis received a reward of 1,600 acres (6.5 km²) of land. He also initially made arrangements to publish the Corps of Discovery journals, but had difficulty completing his writing. In 1807, Jefferson appointed him governor of theLouisiana Territory; he settled in St. Louis.

Lewis' record as an administrator is mixed. He published the first laws in the Upper-Louisiana Territory, established roads and furthered Jefferson's mission as a strong proponent of the fur trade. He negotiated peace among several quarrelling Indian tribes. His duty to enforce Indian treaties was to protect the western Indian lands from encroachment,^[8] which was opposed by the rush of settlers looking to open new lands for settlements. But due to his quarreling with local political leaders, controversy over his approvals of trading licenses, land grant politics, and Indian depredations, some historians have argued that Lewis was a poor administrator. That view has been reconsidered in recent biographies. Lewis's primary quarrels were with his territorial secretary Frederick Bates. Bates was accused of undermining Lewis to seek Lewis's dismissal and his own appointment as governor. Because of the slow-moving mail system, former president Jefferson and Lewis's superiors in Washington got the impression that Lewis did not adequately keep in touch with them.^[17] Bates wrote letters to Lewis's superiors accusing Lewis of profiting from a mission to return a Mandan chief to his tribe. Because of Bates' accusation, the War Department refused to reimburse Lewis for a large sum he personally advanced for the mission. When Lewis's creditors heard that Lewis would not be reimbursed for the expenses, they called Lewis's notes, forcing him to liquidate his assets, including land he was granted for the Lewis and Clark Expedition. One of the primary reasons Lewis set out for Washington on this final trip was to clear up questions raised by Bates and to seek a reimbursement of the money he had advanced for the territorial government. The U.S. government finally reimbursed the expenses to Lewis's estate two years after his death. Bates eventually became governor of Missouri. Though some historians have speculated that Lewis abused alcohol or opiates based upon an account attributed to Gilbert Russell at Fort Pickering on Lewis's final journey,^[18] others have argued that Bates never alleged that Lewis suffered from such addictions and that Bates certainly would have used them against Lewis if Lewis suffered from those conditions.