The Historic Mullan Road Crossed Here: 

At the Idaho/Montana Stateline, U.S. Highway 10 and I-90 follow the general route of the military road located and constructed from 1859-1862 by Lieutenant John Mullan (1830-1909). The road was 624 miles long and connected Fort Walla Walla, Washington Territory and Fort Benton, Montana (then Nebraska Territory).  Congress appropriated $100.000 in the 1850s for construction of a wagon road connecting the head of navigation on the Mississippi - Missouri Rivers with the head of navigation on the Columbia River. The construction crew was made up of 100 military men and 100 civilian construction workers.

Much of the area was covered with dense timber. Since no one, not even the Native Americans going to the plains to hunt ever traveled this way, there were no trails to follow. The road constructed by Lieutenant Mullan was the first road built by engineering principles west of the Mississippi and it provided access to the west for many settlers, prospectors, frontiersmen, and adventurers. The initial Mullan Road was completed in fourteen months after overcoming many difficulties. Mullan, aside from his engineering ability, was a man of considerable insight as evidenced by the following excerpt from his final report. He prophesied “… the locomotive engine will make the passage of the  … wild interior at rates of speed which will startle human credulity.” Indeed two decades later, in 1883, the Northern Pacific Railway constructed a branch line over present day Lookout Pass.

The original Mullan Road went over a pass across the Bitterroot Range on the south side of Ski Lookout Pass aka Runt Mountain, and Mullan named it Sohon Pass for his good friend who traveled with him, artist and linguist Gustavus Sohon. Later it was renamed St. Regis Pass by the Northern Pacific Railway. In Montana, several intact sections of Montana’s earliest road, the Mullan road, exist in close proximity to its descendents the Yellowstone Trail, U.S. Highway 10, and Interstate 90.

Along the Mullan Road at the western base of the Bitterroots, is the town which carries his name, Mullan, Idaho, which grew as a townsite in 1884.