To the Western Ocean: Planning the Lewis and Clark Expedition
In the latter half of the eighteenth century, English, Spanish, and American explorers replaced their French counterparts as the leaders of exploration in the Mississippi and Missouri river valleys. As before, sensational accounts of western voyages continued to generate interest in the region. Increasingly, however, improved scientific methods of surveying, cartography, and natural description allowed for a more accurate picture of the geography of the West. By the end of the century the exact latitudes and longitudes of several important points in the West had been determined.
Thomas Jefferson followed the reports of the explorations of the late 1700s very closely and collected many of the newly published journals and maps, which significantly influenced the planning of the Lewis and Clark Expedition.
In the summer of 1802, Jefferson, in his first term as president of the United States, read Alexander Mackenzie’s account of his journey across Canada to the Pacific. Mackenzie’s recommendation that the British government assume control of the Columbia River and West coast troubled Jefferson. In response, he organized a bold, national enterprise to reach the Pacific. After Congress approved his plan for an expedition, Jefferson appointed his secretary, Meriwether Lewis, to lead the exploring party, later known as the “Corps of Discovery.” Lewis, who had gained firsthand knowledge of the western frontier in the military, was an Albemarle County neighbor of Jefferson. Lewis’s grandfather, Thomas Meriwether, and Jefferson’s father had each been members of the Loyal Company. William Clark, co-captain of the expedition, was a friend of Lewis’s who had been his commanding officer in the army.
Geographic information from British, French, and American explorations in the West and along the Pacific coast shaped Thomas Jefferson’s planning of the Lewis and Clark Expedition. Among the items that Lewis and Clark brought on the expedition were geographical works by Arrowsmith, Mackenzie, Vancouver, Thompson, and Le Page du Pratz, and a new map by Nicholas King commissioned expressly for the expedition. Lewis and Clark also made extensive use of Indian maps. A new map of the West resulted from Lewis and Clark’s expedition—William Clark’s map of 1810, an engraved version of which later appeared in the 1814 published journals of the expedition.