High Quality Content by WIKIPEDIA articles! The Willamette National Forest is a National Forest located in the central portion of the Cascade Range of US state of Oregon. It comprises 1,678,031 acres (6,790.75 km2) making it one of the largest national forests. Over 380,000 acres (694 mi2, 1,540 km2) are designated wilderness which include seven major mountain peaks. There are also several National Wild and Scenic Rivers within the forest. The forest is named for the Willamette River, which has its headwaters in the forest. The forest headquarters are located in the city of Eugene. There are local ranger district offices in McKenzie Bridge, Mill City, Detroit, Sweet Home, and Westfir.