Idaho | State Facts & History

The region was explored by Meriwether Lewis and William Clark in 1805–1806. It was then a part of the Oregon country, held jointly by the United States and Great Britain. Boundary disputes with Great Britain were settled by the Oregon Treaty in 1846, and the first permanent U.S. settlement in Idaho was established by the Mormons at Franklin in 1860.

: https://www.infoplease.com/us/states/idaho