The area of Olympic National Forest is 2,564.4 square kilometers.
Olympic National Forest was created in 1897.
Established as Olympic Forest Reserve in 1897. Name was changed to Olympic National Forest in 1907. Olympic National Park created in 1938. I got this from the U.S. forest service website.
The area of Plumas National Forest is 4,451.542 square kilometers.
The area of Cleveland National Forest is 2,000,000.0 square meters.
The area of Modoc National Forest is 6,695.087 square kilometers.
The area of Chippewa National Forest is 6,474.97 square kilometers.
The area of Stanislaus National Forest is 3,634.478 square kilometers.
The area of Custer National Forest is 5,173.012 square kilometers.
The area of Umatilla National Forest is 7,284.342 square kilometers.
The area of Bitterroot National Forest is 6,422.644 square kilometers.
The area of Inyo National Forest is 24,281.1385344 square meters.
The area of Siuslaw National Forest is 2,549.52 square kilometers.