Between 1804 and 1806, Lewis and Clark made the first systematic reports of the Missouri River based on scientific measurement and observations. They reported on its course, the flora and fauna, its depth and current, tributaries, and inhabitants. They continued to document their observations in the Rocky Mountains and the Pacific Northwest. Lewis and Clark described for science at least 120 mammals, birds, reptiles, and fish, as well as at least 182 plant species. They made the first attempt at a systematic record of the meteorology of the West.

As the expedition began to move up the Missouri River, Lewis focused on the details, such as the animals, the type of rocks, the trees, and grasses. How fast was the current? How high the cliffs? Was that bird or plant different from one known in the East? Lewis described the animals, including the eastern wood rat. The explorers encountered fierce grizzly bears that attacked them. Lewis and Clark were fascinated with the little prairie dogs that built huge underground villages. New species documented included pronghorn antelopes, bighorn sheep, black tailed deer (or mule deer), mountain beaver, white weasel, and coyotes. Lewis and Clark sent back live zoological specimens as well as skins, bones, skeletons, teeth, talons, and horns.

The geographical findings were of scientific 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 River, which proved to be a majestic stream rivaling the Missouri itself rather than a short coastal river. They discovered that contrary to common belief, neither the Missouri nor the Columbia was navigable to its source. 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.

Clark’s drew his relatively crude maps under field conditions, yet they enriched geographical knowledge and stimulated cartographical advances. Of particular importance were three progressively improved maps Clark drew between 1804 and 1810 of the Western United States and lower Canada. According to historical cartographer Carl I. Wheat, the last of the three (c.1809) was "one of the most influential ever drawn" of the United States.

Lewis and Clark also made significant additions to the botanical knowledge of the continent. Jefferson believed that the voyages of discovery would add to the world's supply of food crops and plants beneficial to humankind. Lewis and Clark collected hundreds of plant specimens and recorded information on their habitats, growth, and uses by American Indians. Their collections formed the basis for the first major scientific publication that described and illustrated the plants west of the Mississippi River.

Source: Scientific Encounters
National Park Service, U.S. Department of the Interior, Public Domain