Map of Lewis and Clark's Track

This important map titled A Map of Lewis and Clark's Track Across the Western Portion of North America from the Mississippi to the Pacific Ocean marks the culmination of the Lewis and Clark Expedition, which explored western North America from 1804 to 1806. It also marks the end of the long sought after Northwest Passage, a fabled waterway that many Americans and Europeans hoped would provide an easy passage to the markets of Asia.

At the beginning of the nineteenth century, it was generally thought that the headwaters of the Missouri River were in close proximity to the headwaters of the Columbia River and that only a plateau or a gentle “pyramidal height-of-land” separated the two water systems. Lewis and Clark proved this long-held theory wrong. Rather, they found that a series of rugged mountain ranges divided the continent. Moreover, the streams descending the western slope of the Rockies proved to be unnavigable, shattering the myth of the Northwest Passage for good.

Upon the return of the Expedition to the United States, Clark combined the geographic knowledge he had gained with information gleaned from other travelers into what geographer John Allen calls “an item of superlative craftsmanship and analysis.” Published in 1814, Clark’s map—titled “A Map of Lewis and Clark’s Tracks across the Western Portion of North America”—proved to be a major contribution to American geographic knowledge.

This historic map, copied for engraving and printing by the Philadelphia cartographer Samuel Lewis, revised American ideas of both the Rocky Mountains and the Missouri and Columbia rivers. Unlike previous maps, many of which showed the Rocky Mountains as a single narrow ridge spanning the continent, Clark’s map depicted the Rockies as a complex series of mountain ranges with many outliers. Lewis and Clark also proved wrong the commonly held theory that the Missouri and Columbia were broad navigable streams all the way to their sources.

Clark’s map, one of the most important of the nineteenth century, served as a base upon which the next generation of American cartographers built their knowledge of western geography.

Further Reading:
Allen, John Logan. Lewis and Clark and the Image of the American Northwest. New York, N.Y., 1975.

Moulton, Gary, ed. The Journals of the Lewis and Clark Expedition, Volume 1, Atlas of the Lewis and Clark Expedition. Lincoln Nebr., 1983.

Written by Kathy Tucker, Cain Allen © Oregon Historical Society, 2002, 2004.