Finding the Willamette

In drawing his first map of the continent between the mouth of the Missouri River and that of the Columbia, completed at Fort Clatsop, Clark knew by hearsay that there was “a large river which falls into the Columbia on its south side,” but islands had hidden it from view on the westbound trip. Heading home that spring the Corps missed it again for the same reason, but early on 2 April 1806 some Indians visiting their camp, which was upstream from the tributary in question, happened to mention it. Later that morning Clark picked six of his soldiers, hired an Indian guide, and went back to explore the lowest ten miles of the river that local residents called the Multnomah.

Clark assumed, mainly on the basis of what he had heard, that the source of the Multnomah was “at no great distance from the Spanish Settlements,” around 37° north latitude—almost as far south as Reno, Nevada. He drew it that way on the map he prepared for Nicholas Biddle‘s 1814 edition of the journals. Actually, the Willamette, as it came to be called after 1841, begins in southern Oregon and is only 189 miles long.

Apart from this miscalculation, Clark’s map of the Columbia River basin was remarkably accurate, and it served travelers well for several decades. He had the gift of a great explorer—the ability to sense the land beneath his feet, embrace the moving horizon with his eyes, remember and interpret what Indians had told him, and extrapolate the rest in his imagination.