The Lewis and Clark Expedition passed this place going up the Missouri River on May 30, 1804, on its way to Grinestone Creek, today's Deer Creek, opposite the modern-day town of Mokane. After a wet spring, rain, hail, and strong wind struck at noon, the Missouri ran extra fast, and William Clark wrote that the bottomlands on both sides were full of water; this was the only time the Corps of Discovery saw the river in flood stage. The party passed Auxvasse Creek, which they called the Big Miry River. On May 31, more rain and a strong west wind led the expedition to remain in camp rather than struggle against current and wind. During this layover, Meriwether Lewis explored the countryside and discovered the eastern wood rat, a species new to science. Over the course of the expedition, Lewis described 300 species new to science, including 122 animals such as the grizzly bear, mountain goat, and cutthroat trout, and 178 plants such as lodgepole pine, ponderosa pine, salmonberry, and western wallflower. That day the Corps of Discovery also met a trading party traveling downriver, made up of a French man, a French-Indian man, and an Indian woman, who had been trading at the Big or Grand Osage villages on the Osage River for bear, deer, and beaver skins. They brought troubling news that one group of Osage, displeased by the Louisiana Purchase and the transfer of control to the United States, had burned a letter announcing the change in authority. Because the expedition's goals included promoting fur trade with Indians and asserting American dominion over the new Louisiana Territory, this news disturbed the captains. Lewis and Clark had received instructions from Thomas Jefferson to learn the animals of the country, especially those not known in the U.S. Lewis, the expedition's main naturalist, had prepared before departure by studying astronomy, medicine, and natural science near Philadelphia, while Clark also made important observations in the field. Lewis recorded detailed entries on plant and animal species not yet identified for science, aided by Indians' knowledge of western plants and animals, and the captains also took daily weather readings. Lewis collected skins, horns, bones, and pressed plants for Jefferson, and the expedition even sent live animals back east, including four magpies, a sharp-tailed grouse, and a prairie dog; one magpie and the prairie dog reached Jefferson in Washington. Two species, Lewis' woodpecker and Clark's Nutcracker, were later named in honor of the two explorer-scientists.