Mullan Road was the first wagon road to cross the Rocky Mountains to the Inland of the Pacific Northwest. It was built by U.S. Army troops under the command of Lt. John Mullan, between the spring of 1859 and summer 1860. It led from Fort Benton, which at the time was in the Dakota Territory, then Idaho Territory from July 1863, and Montana Territory beginning in May 1864, and the navigational head of the Missouri River (and once farthest inland port in the world). The road connected 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 present-day Montana, Idaho, and Washington.
This cache is located where the mullan road crosses HWY 26. There is a large pull off with an interpretive sign with lots of information about the Mullan Road and a map of it's route.
Please be careful getting on and off the HWY here as the traffic moves fast.