The results and accomplishments of the Lewis and Clark expedition were extensive. It altered the imperial struggle for the control of North America, particularity in the Pacific northwest, by strengthening the U.S. claim to the areas now including the states of Oregon and Washington. Lewis and Clark achieved an impressive record of peaceful cooperation with the Indians and generated American interest in the fur trade. This had a far reaching effect, since it led to further exploration and commercial exploitation of the West. Lewis and Clark added to geographic knowledge by determining the true course of the Upper Missouri and its major tributaries, and producing important maps of these areas. They forever destroyed the dream of a Northwest Passage, but proved the success of overland travel to the Pacific. The expedition compiled the first general survey of life and material culture of the Native American tribes they encountered.
Lewis and Clark made significant additions to the zoological and botanical knowledge of the continent, providing the first scientific descriptions of many new species of animals, including the grizzly bear, prairie dog, pronghorn antelope, and mountain goat. They made the first attempt at a systematic record of the meteorology of the West, and less successfully attempted to determine the latitude and longitude of significant geographical points.
Lewis and Clark traveled over 8,000 miles in less than 2 1/2 years, losing only one member of their party, at a total cost to the taxpayer of $40,000. By any measure of scientific exploration, the Lewis and Clark expedition was phenomenally successful in terms of accomplishing its stated goals, expanding human knowledge, and spurring further curiosity and wonder about the vast American West.