On July 1, 1908 it gave up some acreage to California National Forest.
In descending order of land area the rest of the counties are Tehama with 7.37%, Shasta with 2.93%, and Humboldt with 0.23%.
[2] There are local ranger district offices in Hayfork and Weaverville.
[3] Its administrative offices reside in Redding, as part of the combined Shasta-Trinity National Forest.
As of 30 September 2008, the Forest has an area of 1,043,677 acres (4,223.61 km²), comprising 47.23% of the combined Shasta-Trinity's total 2,209,832 acres (8,942.87 km²).