Mullan Road

Mullan Road was the first wagon road to cross the Rocky Mountains to the Inland of the Pacific Northwest. It was built by US Army Lieut. John Mullan between the spring of 1859 and summer 1860. It led from Fort Benton, Montana, the navigational head of the Missouri River (and once farthest inland port in the world) to Fort Walla Walla, Washington Territory, near the Columbia River. The road previewed the route approximately followed of modern-day Interstate 15 and Interstate 90 through what are now Montana, Idaho and Washington.

Parts of the Mullan Road can still be traveled. One such section is near Washtucna, Washington.

A segment of the Mullan Road in the vicinity of Benton Lake was listed on the National Register of Historic Places in 1975, and the American Society of Civil Engineers designated it a historic civil engineering landmark in 1977. Three segments of the road in Idaho were also listed on the National Register in 1990. In 2009, the Point of Rocks segment in Montana was also listed on the National Register as part of the Point of Rocks Historic Transportation Corridor.