From this point west to the Idaho line, Us Highway 12 and I-90 follows the route of a military road located and constructed in Montana between 1859 - 62 by Captain John Mullan. The road was 624 miles long and connected Fort Benton, Montana, with Fort Walla Walla, Washington. Originally an Indian trail, Mullan mapped the road over the pass in the 1850s. In 1860, it was incorporated into the military road that would bear his name.
The Captain 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 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 its main line over Mullan Pass.
Mullan himself might have been incredulous had he seen the freight train that crossed this divide in 1865. Seven camels, each laden with 600 pounds of flour, made the trek from Helena to the Deer Lodge area mines. One of the less successful experiments in American transportation history, the dromedary carried tremendous loads, was sure footed, had great stamina, but the horses, mules and oxen of the teamsters and mule packers stampeded at the sight and smell of them. The camels were gone from Montana by 1867.