Significance of the expedition
If Lewis and Clark did not discover the Northwest Passage or a practicable transcontinental channel of commerce, their other accomplishments were formidable. The significance of their exploration extends over a broad and interrelated gamutin geopolitics, westward expansion, and scientific knowledge. From the standpoint of international politics, the expedition basically altered the imperial struggle for control of the North American Continent, particularly the present northwestern United States, to which the U.S. claim was substantially strengthened.
THE westward expansion that ensued in the wake of Lewis and Clark would provide substance to that claim. The wealth of detailed information they acquired about the climate, terrain, native peoples, plants, animals, and other resources of the princely domain they had trodden represented an invitation to occupy and settle it. In their footsteps, came other explorers, as well as trappers, traders, hunters, adventurers, prospectors, homesteaders, ranchers, soldiers, missionaries, Indian agents, and businessmen. They filled in the map, blazed the trails, traded in furs, mined the depths of the earth, tilled the soil, grazed stock, constructed railroads and roads, created towns, founded industries, and formed Territories and States. Ever moving westward, they conquered the land and carried civilization to the shores of the Pacific.
Many of these people followed for part of the way the Missouri River route that Lewis and Clark had pioneereda waterway that became one of the major westward routes, though the complications of traveling it by steamboat restricted the flow of traffic to its lower reaches and rendered it less useful than the major overland trails.
THE initial spur to westward expansion was the news the explorers brought back about the rich potentialities of the western fur trade, which were concentrated in the Upper Missouri-Yellowstone River-Rocky Mountain area. This trade was the first means of exploiting the resources of the newly discovered land. Trappers and traders were the first to penetrate it in detail, and these mountain men laid the groundwork for the miners and settlers who followed. 
Reacting to newspaper and word-of-mouth accounts of the reports of Lewis and Clark to Jefferson and others of the wealth in furs and a natural all-water route of access, the Missouri, adventurers and trappers flocked to St. Louis in the winter and spring of 1806-7. But, as in the later days of the mining rushes, most of those who chose to operate independently were to meet frustration. They were forced to confine their activities to the Lower Missouri or join one of the large and well-organized companies that soon sprang up and monopolized the Rocky Mountain fur trade. Only they possessed the necessary capital to finance the long journeys necessary to reach the hunting grounds and send out parties of sufficient size to ward off Indian attacks.
BUT such hostilities, mainly limited to spasmodic outbreaks of the Teton Sioux, Arikaras, and Blackfeet, were undoubtedly far less severe than they might have been were it not for the reservoir of goodwill the expedition had left with nearly all the western tribes. This reservoir, which Clark deepened during his long and distinguished post-expedition career as Superintendent of Indian Affairs in St. Louis, contributed to the success of the early westward movement.
Blending fairness, honesty, and strength with patience, respect, and understanding, Lewis and Clark recognized the personal dignity of the Indians, honored their religion and culture, sincerely proffered aid from the U.S. Government, and tried to establish intertribal peace. Masters of primitive psychology, they instinctively and unerringly always seemed to make the right decision and rarely offended the natives.
Tragically, this heritage of friendliness was not to prevail for more than a few decades. As the westward advance of the Nation burgeoned in the 1840's, the two civilizations clashed. Frontiersmen, eager for land and gold, considered the Indians as "uncivilized" obstacles in their path. The decency and integrity demonstrated by Lewis and Clark in their dealings with them gave way to disrespect and dishonor. In the Government's attitude, honesty too often yielded to deception and altruism to self-interest. Mortal conflict ensued that crushed the Indian way of life [see Soldier and Brave (New Edition), Vol. XII in this series].
THE Lewis and Clark Expedition also made major contributions to the fields of geography-cartography, ethnography, and natural history.  Scientists were kept busy for a long time digesting the mass of raw information, studying plant and animal specimens, analyzing descriptions and translating them into the appropriate technical language, and classifying and correlating data.
Neither of the two leaders were trained scientists by the standards of their day. Many of their geographic calculations were faulty because they often relied on dead reckoning and did not properly adjust their chronometer and other instruments. Their descriptions of plants and animals lacked professional nomenclature and polish. But, considering the time in which they lived and the circumstances they faced in the field, they demonstrated remarkable competence.
Except in cartography, Lewis was primarily responsible for most of the scientific contributions. He was better educated than Clark and during 2 years of residence with President Jefferson prior to the expedition had enjoyed access to his fine library and been able to draw on his extensive knowledge of zoology and botany. Lewis had also enjoyed the benefit of a cram course in science at Philadelphia and Lancaster that Jefferson arranged for him.
THE geographical findings were in themselves of outstanding significance. Lewis and Clark determined the true course of the Upper Missouri and its major tributaries. They discovered that a long, instead of short, portage separated it from the Columbia, which proved to be a majestic stream rivaling the Missouri itself rather than a short coastal river. Neither the Missouri nor the Columbia was found to be navigable to its source, as many had believed. The explorers also learned that, instead of a narrow and easily traversed mountain range, two broad north-south systems, the Rockies and the Cascades, represented major barriers.
Passing for the most part through country that no Americans and few white men had ever seen, the two captains dotted the map with names of streams and natural features. Some of the designations that have survived to this day include the Jefferson, Madison, Gallatin, Milk, Marias, and Judith Rivers, Beaverhead Rock, Rattlesnake Cliffs, White Bear Islands, York Canyon, and Baptiste Creek. Unfortunately, many other names that were best-owed have faded out of existence.
Clark made his scientific mark primarily in the field of cartography, for which his training consisted mainly of some experience in practical surveying and a limited amount of Army mapping. Yet his relatively crude maps, prepared under field conditions, enriched geographical knowledge and stimulated cartographical advances. 
Of particular importance were the three progressively improved maps Clark drew between 1804 and 1810 of the Western United States and lower Canada.  These were mainly based on the observations of the two captains, data provided by the Indians, earlier maps of the West, and the journals of preceding explorers. According to historical cartographer Carl I. Wheat, the last of the three (ca. 1809) was of "towering significance" and was "one of the most influential ever drawn" of the United States. Although deficient in its nonexpedition data, provided to Clark by others, for three decades it represented some of the best knowledge available about the West and practically all other maps were based on or influenced by it. Also valuable to geographers and cartographers were the detailed local and regional maps that Clark sketched in his journals or on separate sheets of paper.  They provided valuable information on hydrography and relief.
THE second scientific field on which the Lewis and Clark Expedition exerted a major impact was ethnography. Although the two captains' comprehensive descriptions of the natives and their way of life contained some errors and misconceptions, as a whole they were so astonishingly accurate and complete that they provided a basic document for western ethnologists.
Previously, almost nothing had been known of the Indians westward from the Mandan villages, in present North Dakota, to the Upper Columbia. Native groups residing in that area, whom the explorers were undoubtedly the first white men to encounter and describe, included the Northern Shoshoni, Flatheads, Nez Perces, Cayuses, Yakimas, and Walla Wallas. Although the expedition did not meet any Crows, their presence was noted.
Even for those tribes that traders had contacted and casually reported onthose on the Lower Missouri from St. Louis to the Mandan villages and those at the mouth of the ColumbiaLewis and Clark furnished a far more complete body of data than had ever before been recorded. They also sent back from Fort Mandan, in present North Dakota, or brought back to Washington, D.C., a number of ethnological specimens. 
THE final category of scientific knowledge that the exploration enriched was natural history.  Usually based on their own observations but sometimes on Indian information, the two captains described hundreds of species of fishes, reptiles, amphibians, mammals, birds, plants, trees, and shrubs. Some were completely new to the world of science; others had never previously been encountered in North America; or earlier descriptions were sketchy and inadequate. In these categories, among mammals alone, are the pronghorn (antelope), bighorn sheep, mountain beaver, black-tailed prairie dog, white weasel, mountain goat, grizzly bear, coyote, and various species of deer, rabbit, squirrel, fox, and wolf. In addition to their descriptions, Lewis and Clark also sent back a large number of zoological specimens, including a few live ones as well as skins, bones, skeletons, teeth, talons, and horns, and in addition a diversity of botanical items. 
Last Updated: 22-Feb-2004