a wagon route (now commonly called the Mullan Road) between Fort Benton (Montana) and Fort Walla Walla (Washington). Lieutenant Mullan, a topographical engineer, began gathering information in 1854. Delayed by the Yakima War which ended in 1858, construction began in 1859 from Fort Walla Walla in what was then Washington Territory. Lieutenant Mullan commanded a workforce of more than 200, including civilian workers, surveyors, engineers, and soldiers who carved a road across the region. After the difficult project was completed in 1860, floods wiped out substantial stretches of the road. It was re-routed in 1861. Floods again damaged the road, and ultimately, no provision for maintenance was provided. Although the road was never heavily used by the military, it was an important conduit for civilian passage, which hastened settling of the northwestern United States. In the first year after completion, it was used by an estimated 20,000 people, 6,000 horses and mules, 5,000 cattle and 83 wagons. The discovery of gold in North Central Idaho in 1860 by Capt. E.D. Pierce contributed to this usage, making Lewiston, Washington Territory, the largest town in the Pacific Northwest and the capital of the new Idaho Territory beginning July 4, 1863. The Mullan Road helped Walla Walla become the largest town in Washington Territory by 1870, with a population of 1,394. The road continued to serve as an important route until the completion of the Northern Pacific Railroad in 1883 provided faster and more convenient access to the region. Route of the Mullan Road From the origin at Fort Benton, Montana, the Mullan Road proceeded: West from Fort Benton, it passed north of Great Falls Dropping south to cross the continental divide west of Helena (following a path through Mullan Pass at , immediately north of that now traveled by US 12) Just west of Garrison, it joined the route used by the future US 10 (present-day Interstate 90) (similar to the US 12 transition to join Interstate 90 today) Along the Clark Fork River near the ghost town of Bearmouth, also along the future US 10 It remained with the future US 10 route as it passed through Missoula, proceeding west through Montana. The Mullan Road through the Missoula Valley, slightly south of the former US 10 and still in use today as S-263, fostered rapid growth for the burgeoning city, and allowed the U.S. Army to establish Fort Missoula in 1877.