The Weminuche Wilderness is a wilderness area in southwest Colorado managed by the United States Forest Service as part of the San Juan National Forest on the west side of the Continental Divide and the Rio Grande National Forest on the east side of the divide. The Weminuche Wilderness was designated by Congress in 1975, and expanded by the Colorado Wilderness Acts of 1980 and 1993. It is located 4 mi southeast of the town of Silverton, 17 mi northeast of Durango, and 8 mi west of South Fork. At 499771 acre, it is the largest wilderness area in the state of Colorado. Elevation in the wilderness ranges from 7700 ft along the Animas River to 14093 ft at the summit of Windom Peak. The Weminuche Wilderness is dissected by a narrow north-south corridor within the Animas River Gorge through which the Durango and Silverton Narrow Gauge Railroad travels between Silverton and Durango. To the west of this corridor are the West Needle Mountains. To the east lie the Needle Mountains and the bulk of the wilderness. Two train stops within the gorge allow hikers access into the Needle Mountains. The Wilderness was named after the Weminuche Native Americans.

Geology

The surface geology of the Weminuche Wilderness is characterized by two geologic provinces. The western third of the wilderness is within the Needle Mountains Proterozoic complex while the remainder of the wilderness is within the San Juan volcanic field. The Laramide Orogeny, which began approximately 80 million years ago in the Late Cretaceous, resulted in significant regional uplift. A dome 100 mi wide lifted rock more than 10000 ft in the western third of the wilderness. Pushed up were Proterozoic igneous and metamorphic rock and overlying, younger Paleozoic and Mesozoic sedimentary rock, as well as Cenozoic volcanic rock. Erosion has removed the overlying rock and today the Proterozoic rock is exposed, forming the high, jagged, Needle Mountains. The highest peaks in the wilderness are in the Needle Mountains. These peaks include three fourteeners: Windom Peak, Mount Eolus, and Sunlight Peak. Eolus granite is a common rock in the Needle Mountains and these fourteeners are composed of this intrusive igneous rock. To the east lies the San Juan volcanic field. While this region was also uplifted during the Laramide Orogeny, additional mountain building occurred as Tertiary volcanism deposited lava and ash, which in some places was over 6000 ft thick. These volcanic rocks overlay Cretaceous sedimentary rock, which is exposed in only a few places on the southern edge of the wilderness. The Weminuche Wilderness was glaciated during the Pleistocene and the current landscape is dominated by glacial landforms including horns, arêtes, cirques, tarns, moraines, and U-shaped valleys.

Flora and fauna

At lower elevations, particularly along the southern side of the wilderness, are montane forests with stands of ponderosa pine and Douglas fir and thickets of Gambel oak. Higher and widespread through the wilderness are subalpine forests dominated by Engelmann spruce and subalpine fir. Stands of aspen occur in the wilderness on historically disturbed sites in both the montane and subalpine zones. Above tree line, which in the wilderness is at an elevation of about 11500 ft, is alpine tundra dominated by grasses and forbs, along with extensive thickets of willow. Infestations of spruce beetle have ravaged the Engelmann spruce within the wilderness. Substantial outbreaks began in the late 1990s and have general moved from southeast to northwest through the wilderness. As of 2017, over 120000 acre of forest had been impacted. In places, particularly in older stands, the kill has been nearly 100%. The wilderness is known for its herds of elk. Other mammals include mule deer, bighorn sheep, moose, marmots, and pikas. Also present are black bears, mountain lions, re-introduced lynx, bobcats, and coyotes. Mountain goats have been introduced in the wilderness and are now common at higher elevations, particularly in the Needle Mountains. There are concerns over the environmental impact of these non-native goats, particularly their harm to native bighorn sheep populations. Current management in the Weminuche Wilderness allows the mountain goats to persist. This is in contrast to active efforts to eliminate or reduce non-native mountain goat populations in other protected areas such as Rocky Mountain National Park, Grand Teton National Park, and Olympic National Park.

Hiking

Travel through the wilderness is limited to those on foot and horseback. There are nearly 500 mi of interconnected trails in the wilderness, which provide for multiple options for both day and multi-day trips. Forming the backbone to this network is the Continental Divide Trail, which traverses the wilderness 83 mi from Wolf Creek Pass in the southeast to Stony Pass in the northwest. This network of trails is accessed from over 30 trailheads located around the periphery of the wilderness. Two of these trailheads are the Needleton and Elk Park stops on the Durango and Silverton Narrow Gauge Railroad, which provide the most direct access to the highly visited Needle Mountains.

Chicago Basin

The most popular trail in the wilderness is the Needle Creek Trail (Forest Trail 504) which begins at the Needleton train stop and leads southeast 6 mi up into Chicago Basin. From Chicago Basin, where camping is permitted, climbers can reach three fourteeners (Windom Peak, Mount Eolus, and Sunlight Peak) and several thirteeners via day hikes. Chicago Basin sees approximately 10,000 visitor use days each year, most seeking to climb one or more fourteeners, and the area can be crowded. Environmental impacts have resulted in use restrictions in the Chicago Basin area that go beyond regulations applied to the wilderness as a whole.

Continental Divide Trail

Beyond the Chicago Basin area, trails in the wilderness see much less traffic and solitude can be found. The Continental Divide Trail (CDT) is a 3100 mi National Scenic Trail that stretches from Mexico to Canada and passes through the length of the Weminuche Wilderness. The CDT enters the wilderness at Wolf Creek Pass on U.S. Highway 160. The trail then weaves northwest 83 mi through the wilderness to Stony Pass on San Juan County Road 3 near Silverton. Following the crest of the San Juan Mountains, this trail offers hikers and those on horseback expansive views of nearby peaks and distant mountain ranges. This is a high path with an average elevation of 11,900 ft, and it rarely dips below tree line. Less than a quarter of the trail passes through forest. More common are long stretches across alpine tundra, rocky slopes and ridges, and subalpine meadows. The highpoint of the trail is at 12850 ft on the ridge below South River Peak and the lowest point is where the trail drops to the headwaters of the Los Pinos River at 10500 ft. Altogether, there is 16400 ft of elevation gain and 14700 ft of elevation loss on a southeast-to-northwest trip. The Stony Pass Trailhead is on a four-wheel drive road and has limited parking. To facilitate transportation, there are other nearby trailheads that can be used to exit the Weminuche Wilderness. These include the Elk Park train stop, the Molas Pass Trailhead, the Highland Mary Trailhead, and the Silverton Trailhead just outside the town of Silverton.

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