Their mission was to explore the territory of the Louisiana Purchase, establish trade with, and sovereignty over the natives near the Missouri River, and claim the Pacific Northwest and Oregon Country for the United States before European nations.

Meriwether Lewis was born August 18, 1774,[5] on Locust Hill Plantation in Albemarle County, Colony of Virginia, in the present-day community of Ivy.

Lewis resided in the presidential mansion and frequently conversed with various prominent figures in politics, the arts and other circles.

[12] He compiled information on the personnel and politics of the United States Army, which had seen an influx of Federalist officers as a result of "midnight appointments" made by outgoing president John Adams in 1801.

[16] In addition, Jefferson placed special importance on declaring U.S. sovereignty over the Native Americans along the Missouri River.

[16] When they left Fort Mandan in April 1805 they were accompanied by the 16-year-old Shoshone woman, Sacagawea, the wife of the French-Canadian fur trader, Toussaint Charbonneau.

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.

The success of their journey helped to strengthen the American concept of "manifest destiny" – the idea that the United States was destined to reach across North America from the Atlantic to the Pacific.

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.

Because of Bates' accusation, the War Department refused to reimburse Lewis for a large sum he personally advanced for the mission.

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 reimbursement of the money he had advanced for the territorial government.

He hoped to resolve issues regarding the denied payment of drafts he had drawn against the War Department while serving as governor of the Upper Louisiana Territory, leaving him in potentially ruinous debt.

[30] Mrs. Griner claimed Lewis acted strangely the night before his death: standing and pacing during dinner and talking to himself in the way one would speak to a lawyer, with face flushed as if it had come on him in a fit.

She continued to hear him talking to himself after he retired, and then at some point in the night, she heard multiple gunshots, a scuffle, and someone calling for help.

Another account claims the servants found him in the cabin, wounded and bloody, with part of his skull gone, where he lived for several hours.

[citation needed] When William Clark and Thomas Jefferson were informed of Lewis's death, both accepted the conclusion of suicide.

Based on their positions and the lost Lewis letter of mid-September 1809, historian Stephen Ambrose dismissed the murder theory as "not convincing".

[34] From 1993 to 2010, about 200 of Lewis's kin (through his sister Jane, as he had no children) sought to have the body exhumed for forensic analysis, to try to determine whether his death was a suicide or murder.

[35] Historian Paul Russell Cutright wrote a detailed rebuttal of the murder/robbery theory, concluding that it "lacks legs to stand on".

Leading Lewis scholars Donald Jackson, Jay H. Buckley, Clay S. Jenkinson, and others have stated that, regardless of their leanings or beliefs, the facts of his death are not known, there are no eyewitnesses, and the reliability of reports of those in the place or vicinity cannot be considered certain.

Author Peter Stark believes that post-traumatic stress disorder may have been a contributor to Meriwether Lewis's condition after spending months traversing hostile Indian territory, particularly because travelers coming afterward exhibited the same symptoms.

[37] According to research from author Thomas Danisi, Lewis's self-inflicted gunshot wounds were not the result of murder or attempted suicide, but a combination of a severe malarial attack, a deranged state of mind, and intense pain.

Lemuel Kirby, a stonemason from Columbia, Tennessee, chose the design of a broken column, commonly used at the time to symbolize a life cut short.

In 1925, in response to the committee's work, President Calvin Coolidge designated Lewis's grave as the fifth National Monument in the South.

A bronze bust of Lewis was dedicated at the Natchez Trace Parkway for a planned visitor center at the gravesite.

[13] Four years after Lewis's death, Thomas Jefferson wrote: "Of courage undaunted, possessing a firmness & perseverance of purpose which nothing but impossibilities could divert from its direction, careful as a father of those committed to his charge, yet steady in the maintenance of order & discipline, intimate with the Indian character, customs & principles, habituated to the hunting life, guarded by exact observation of the vegetables & animals of his own country, against losing time in the description of objects already possessed, honest, disinterested, liberal, of sound understanding and a fidelity to truth so scrupulous that whatever he should report would be as certain as if seen by ourselves, with all these qualifications as if selected and implanted by nature in one body, for this express purpose, I could have no hesitation in confiding the enterprise to him.

[48][49] In 2004, the American elm cultivar Ulmus americana 'Lewis & Clark' (selling name Prairie Expedition) was released by North Dakota State University Research Foundation in commemoration of the Lewis & Clark expedition's bicentenary;[50] the tree has a resistance to Dutch elm disease.

Geographic names that honor him include: Fort Clatsop was the encampment of the Lewis and Clark Expedition in the Oregon Country near the mouth of the Columbia River during the winter of 1805–1806.

Located along the Lewis and Clark River at the north end of the Clatsop Plains approximately 5 miles (8.0 km) southwest of Astoria, the fort was the last encampment of the Corps of Discovery, before embarking on their return trip east to St. Louis.