Northwest Passage?
Since the late 1400s and the time of Columbus, explorers from all over the world eagerly sought to discover the legendary water route, or "Northwest Passage," that was rumored to bisect the resource rich interior of the North American continent.
As late as 1803 President Jefferson's long list of instructions to Captain Meriwether Lewis included:
"The object of your mission is to explore the Missouri River" and to determine
"the most practicable water communication across this continent for the purpose of commerce."
But on July 4th, 1806, while travelling through the Missoula Valley on his return to St. Louis, a disappointed Captain Lewis finally concluded that the most practical route between the Missouri River (east of the Rocky Mountains) and the Columbia River (west of the Rocky Mountains) was by land, following hundreds of miles of trail over difficult terrain. Lewis and Clark's western explorations helped put the 300-year-old "Northwest Passage" myth to rest.
After Lewis & Clark
Fifty three years later (1859) Lieutenant John Mullan was put in charge of constructing a primitive military road between the Missouri and Columbia Rivers. The road would also allow important supplies to be transported to the new settlements between the two great rivers. Mullan first determined that Lewis and Clark's suggestions for a road were unfeasible. Mullan's well researched route was much more practical, but was still a whopping 624 miles long, and often took over two months to travel by wagon. Sections of the Mullan Road are still in use in Washington, Idaho and Montana - including Missoula.
From the Plaque