Bannock Pass was a traditional Indian route that provided access from Montana's buffalo country to the Snake and Salmon river fishing streams. Hudson's Bay Company trapping expeditions came this way after 1822, and prospectors followed in search of mines. In 1877, Nez Perce war combatants returned from Montana to Idaho through Bannock Pass on their way from the Big Hole battleground to Yellowstone Park and Canada. From 1910 to 1939, railroad trains from Dillon to Salmon steamed through here, and old Gilmore and Pittsburgh railroad tunnels and grades still can be seen from this highway.