Editing Thomas Jefferson (section)

===Expeditions===
{{Main|Lewis and Clark Expedition|Dunbar and Hunter Expedition|Red River Expedition (1806)|Pike Expedition}}
[[File:Lewis and clark-expedition.jpg|thumb|alt=Corps of Discover on river boat October 1805|''Lewis and Clark on the Lower Columbia'', a 1905 portrait by [[Charles Marion Russell]] depicting [[Lewis and Clark Expedition|Lewis and Clark's expedition]] on the [[Columbia River]] during Jefferson's presidency]]

Jefferson anticipated further westward settlements due to the Louisiana Purchase and arranged for the exploration and mapping of the uncharted territory. He sought to establish a U.S. claim ahead of competing European interests and to find the rumored [[Northwest Passage]].<ref name="Ambrose76">[[#Ambrose|Ambrose, 1996]], pp. 76, 418.</ref> Jefferson and others were influenced by exploration accounts of [[Antoine-Simon Le Page du Pratz|Le Page du Pratz]] in Louisiana (1763) and [[James Cook]] in the Pacific (1784),<ref>[[#Ambrose|Ambrose, 1996]], p. 154.</ref> and they persuaded Congress in 1804 to fund an expedition to explore and [[:File:Lewis and Clark Expidition Map.jpg|map]] the newly acquired territory to the Pacific Ocean.<ref>[[#Rodriguez|Rodriguez, 2002]], pp. xxiv, 162, 185.</ref>

Jefferson appointed secretary [[Meriwether Lewis]] and acquaintance [[William Clark]] to lead the [[Corps of Discovery]] (1803–1806).<ref>[[#Rodriguez|Rodriguez, 2002]], pp. 112, 186.</ref> In the months leading up to the expedition, Jefferson tutored Lewis in the sciences of mapping, botany, natural history, mineralogy, and astronomy and navigation, giving him unlimited access to his library at Monticello, which included the largest collection of books in the world on the subject of the geography and natural history of the North American continent, along with an impressive collection of maps.<ref>[[#Ambrose|Ambrose, 1996]], pp. 54, 80.</ref> The expedition [[Timeline of the Lewis and Clark Expedition|lasted from May 1804 to September 1806]] and obtained a wealth of scientific and geographic knowledge, including knowledge of many Indian tribes.<ref>[[#Ambrose|Ambrose, 1996]], pp. 154, 409, 512.</ref>

Jefferson organized three other western expeditions: the [[Dunbar and Hunter Expedition|William Dunbar and George Hunter Expedition]] on the [[Ouachita River]] (1804–1805), the [[Red River Expedition (1806)|Thomas Freeman and Peter Custis Expedition]] (1806) on the [[Red River of the South|Red River]], and the [[Pike Expedition|Zebulon Pike Expedition]] (1806–1807) into the Rocky Mountains and the Southwest. All three produced valuable information about the American frontier.<ref>[[#Berry|Berry, 2006]], p. xi.</ref> This interest also motivated Jefferson to meet the Prussian explorer [[Alexander von Humboldt]] several times in June 1804, inquiring into Humboldt's knowledge of New Spain's natural resources, economic prospects, and demographic development.<ref>{{ cite book | last=Daum | first=Andreas W.|author-link=Andreas Daum | year=2024 | title=Alexander von Humboldt: A Concise Biography | location=Trans. Robert Savage. Princeton, N.J. | publisher=Princeton University Press |pages=80 | isbn=978-0-691-24736-6 }}</ref>