Mapping the Expedition
From Hand-Drawn Maps to GIS
 When the Corps of Discovery set out, maps were laboriously hand-drawn. Often they were inaccurate, because the technology of the time was rudimentary and required precise calculations based on a limited understanding of the mapper's current location.
Maps built with GIS and interactive layers of geographic data are now replacing those hand-inked illustrations. As an integrating technology, GIS is making it possible to expand on the expedition’s "geographic transect" across a continent in ways Lewis and Clark would never have dreamed.
Map of western North America circa 1802, "Terra Incognita."
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Map of the Columbia trail, circa 2003, courtesy of David Rumsey.
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