Designated by Congress in 1968, Mt. Jefferson Wilderness is located in the northwestern part of the state, sharing its northeastern border with the Warm Springs Indian Reservation. Mt. Jefferson itself is the pinnacle feature of the High Cascades. With elevations over 10,000 feet Mt. Jefferson provides one of the steepest and most challenging summit for hikers in the state of Oregon. Five glaciers exist on the slopes of the mountain: Whitewater, Waldo, Milk Creek, Russell and Jefferson Park.
The Mt. Jefferson Wilderness area stretches 402,525 acres and encompasses approximately 190 miles of hiking trails, 40 miles of which are part of the Pacific Crest Scenic Trail. There are over 150 lakes in the area, many of them heavily populated with trout. Jefferson Park, Marion Lake, Pamelia Lake, and Jack Lake are among the most popular destinations.
Much of the terrain is characterized by wide open fields with scattered tree cover but there are also talus slopes, rocky outcroppings and alpine meadows. Common trees in the area include: Douglas-fir, silver fir, sub-alpine fir, mountain hemlock, lodgepole pine, ponderosa pine and several species of cedar. Vine maple, huckleberry and rhododendron can also be found.
A few of the most common access points to enter the Mt. Jefferson Wilderness area include the Pacific Crest Scenic trailhead (#2000), the Summit Trial (#4041) and the Marion Lake Trail (#3436). Self-issue entry permits are required for entry into the Mt. Jefferson Wilderness area between Memorial Day and October 31.