On July 18, 1805, Meriwether Lewis recorded passing the entrance of a considerable, bold, clear stream nearly as wide as the Missouri at that place and named it Dearborn's River in honor of Secretary of War Henry Dearborn. The mouth of the Dearborn River lies on the opposite side of the river about one-quarter mile upstream from this location. The river's drainage provided a natural roadbed from the crest of the Continental Divide into the Northern Plains for mountain nomadic Indian tribes living west of the divide, who knew this passage as the Road-to-the-Buffalo. It also offered a route from the Missouri River to rivers on the Pacific side of the divide, suggesting the possibility of a water route across the continent, a primary objective of the Corps of Discovery. Lewis and Clark had heard of this route while wintering at Fort Mandan in 1804–1805, though only in sketchy detail. After camping downstream on the night of July 17, 1805, very near the present day Dearborn Inn, the party passed the river's mouth early on the morning of July 18 without recognizing its importance. During the winter of 1805-1806 at Fort Clatsop, Lewis and Clark concluded that this was the river they had previously been told about, and Lewis returned along the Road-to-the-Buffalo in 1806.