The pass gained importance in the 18th century, when the Lemhi Shoshone acquired horses and used the route to travel between the two main parts of their homeland.

[4] This was the first time that white men had seen present-day Idaho: We proceeded to the top of the dividing ridge from which I discovered immense ranges of high mountains still to the West of us with their tops partially covered in snow The next day Lewis met Cameahwait and his band of Shoshone, and returned with them across the pass to meet Clark.

[3] The pass derives its present name from Fort Lemhi, founded in 1855 by Mormon missionaries who were the first non-Indians to establish a sustained relationship with the Salmon River Indian people.

[6] The deposits lie within quartz veins hosted in Precambrian rock with minerals such as hematite, apatite, feldspar, thorite and monazite present.

[7] Neodymium, cerium, gadolinium, yttrium, and dysprosium are the top lanthanide minerals recorded to be attainable in the Lemhi Pass.