Are you looking for a good hike in Southern Oregon, perhaps one that takes you up an extinct shield volcano? Well if you are grab your CamelBak, other Hydration Pack or Hydroflask and get ready for a difficult, but rewarding hike.

Mount Thielsen, or Big Cowhorn, is an extinct shield volcano in the Oregon High Cascades, near Mount Bailey. It is located near Diamond Lake and north of Crater Lake National Park, in the Umpqua National Forest. Mt. Thielsen is a stratovolcano like many other Cascade peaks, but unlike most, Thielsen’s 9,184-foot summit has been fractured and eroded into a pointy horn of rock — with no crater. Distinctive for its precipitous slopes and jagged, horned top, it has been eroded by glaciers, though volcanic ash has covered parts. After Mount Thielsen stopped erupting, subsequent glacial erosion has formed a horn-like shape. The spire-like shape of Thielsen attracts lightning strikes and causes the formation of fulgurite, an unusual mineral.

The prominent horn forms a centerpiece for the Mount Thielsen Wilderness, an area with many recreational activities. A trail from Oregon Highway 138 leads up the west side of Thielsen, and is about an 8.8 miles round-trip hike with an approximate elevation gain of 3,782 feet.

The Hike

  • Approximate Distance (Round Trip): 9.8 miles / 15.8 km
  • Elevation Gain: 3,782 feet / 1,153 meters
  • Minimum Elevation: 5,400 feet / 1,646 meters
  • Maximum Elevation: 9,182 feet / 2,799 meters

The trail leads through lodgepole pine for the first mile with the timberline at approximately 7200 feet, and inviting glimpses of Mt. Thielsen are evident as one progresses up the trail. After about 1.6 miles, just beyond the Spruce Ridge Trail junction, hikers are rewarded with a beautiful view of Mt. Thielsen. After about 2.9 miles, jus as you reach the Pacific Crest National Scenic Trail, the glacial features of this volcanic peak loom before you.From the Pacific Crest National Scenic Trail, a scramble trail works its way to the spire pointed peak at 9,182 feet elevation. The trail is a steep climb, particularly above timberline beyond which there are no markers. Keep in mind the last 200 feet is a difficult hand-over-hand climb that requires technical Class-4 rock climbing abilities to the summit. A belayed ascent (rope and harness with protection) is recommended, as is a helmet. However at an elevation of approximately 9182 feet the hiker/climber can enjoy views of Diamond Lake, Mt. Bailey, and Mt. Mazama. Please remember caution, and proper climbing equipment, and climbing skills are highly recommended for climbing on the loose rocky slopes.

This trail is used in the winter time by Nordic skiers up to the Pacific Crest National Scenic Trail.Even if you don’t have the proper equipment or skills to climb the last 200 feet this is still a hike worth doing, as you are still rewarded with fantastic views of Mt. Thielsen and the surrounding area.

Please also keep in mind that the Diamond Lake area has many thunderstorms in the summer. It is very wise to descend when threatened with thunderstorms. Mt. Thielsen is often called the “lightning rod of the Cascades” for good reason, so be careful if there are thunderstorms in the area.

The Trailhead:

Go 1.5 miles north of the Highway 230/Highway 138 road junction near Diamond Lake. The trailhead parking lot is located along the east side of Highway 138. A USFS Northwest Forest Pass is required to park at this trailhead. Umpqua National Forest Recreation Map reference number is L-6. Located at Township 28 south, Range 5 1/2 east, Section 16.

Fees: $5 fee or Northwest Forest Pass

Please note: The Northwest Forest Pass is required at some trailheads on National Forests in Oregon and Washington. These passes are distinct from the wilderness permits.

U.S. Forest Service Northwest Forest Pass

Here is a link to a U.S. Forest Service website that describes some of the various passes available so you can choose the best option for you. Recreation Passes of the Northwest.

Mt Thielsen Peak Hike route

This map is the approximate route of the trail, and is not a GPS rendering of the trail and is not the exact route.
View Mt Thielsen Peak Hike/Climb in a larger map


YouTube Video of the Mt Thielsen Hike from sadian24