Chelan National Forest was established in Washington by the U.S. Forest Service on July 1, 1908 with 2,492,500 acres (10,087 km2) from a portion of Washington National Forest. On July 1, 1921 it absorbed the first Okanogan National Forest, but on March 23, 1955 the name was changed back to Okanogan.
References
Chelan National Forest Wikipedia(Text) CC BY-SA