The Lemhi Pass is a very historically significant site in the history of the United States. It is a part of the Lewis and Clark Expedition, used as a route to cross the Continental Divide. It was also the place where the white men had first seen the present-day Idaho.

The Lemhi Pass was commonly used by the Lemhi Shoshone to travel between the two major parts of their homeland. It was also used as a western border mark during the 1803 Louisiana Purchase and 1846 Oregon Treaty. It is also the richest site of thorium deposits in all of the United States.

Declared as a National Historic Landmark in 1960, the Lemhi Pass is now under the care of the National Park Service system.