Umpqua National Forest, in southern Oregon's Cascade Range, covers an area of 983,129 acres (3,978.58 km2) in Douglas, Lane, and Jackson counties, and borders Crater Lake National Park. The four ranger districts for the forest are the Cottage Grove, Diamond Lake, North Umpqua, and Tiller ranger districts. The forest is managed by the United States Forest Service, headquartered in Roseburg.

Mount Thielsen, or Big Cowhorn, is an extinct shield volcano in the Oregon High Cascades, near Mount Bailey. Because eruptive activity ceased 250,000 years ago, glaciers have heavily eroded the volcano's structure, creating precipitous slopes and a horn-like peak. The spire-like shape of Thielsen attracts lightning strikes and creates fulgurite, an unusual mineral. The prominent horn forms a centerpiece for the Mount Thielsen Wilderness, a reserve for recreational activities such as skiing and hiking. Thielson is one of Oregon's Matterhorns.