Southwestern Colorado · 35 million years in the making
San Juan Mountains
Colorado's most dramatic mountain range, born from ancient volcanoes
Volcanic Origins
Fire, ice, and deep time
The San Juan Mountains formed roughly 35 million years ago through a series of violent volcanic eruptions that deposited thousands of feet of ash, lava, and debris across southwestern Colorado. Over the millennia that followed, glaciers carved the volcanic rock into the jagged peaks, deep valleys, and U-shaped cirques that define the range today. The result is some of the most dramatic mountain scenery in all of the Rocky Mountains.
The range contains some of Colorado's highest and most rugged terrain. Seven fourteeners -- peaks above 14,000 feet -- stand within 20 miles of Purgatory Resort. Hundreds of additional summits exceed 13,000 feet, separated by alpine basins, high passes, and valleys that remain snowbound well into summer. The mountains stretch from Ouray and Telluride in the north to Pagosa Springs in the east and the New Mexico border to the south, covering thousands of square miles of backcountry.
Protected Lands
Half a million acres of wilderness
The Weminuche Wilderness is the largest designated wilderness area in Colorado, spanning roughly 500,000 acres across the heart of the San Juans. No roads, no motorized equipment, no structures -- just trail, rock, and sky. The wilderness contains dozens of alpine lakes, several fourteener summits, and hundreds of miles of backcountry trail that see few visitors even in peak season.
The broader San Juan National Forest, established in 1905 by President Theodore Roosevelt, surrounds the wilderness and provides the managed forest land where Purgatory Resort and many popular trailheads are located. The Colorado Trail -- the 486-mile hiking route from Denver to Durango -- passes through the range on its final leg, with some of its most challenging and scenic sections crossing high passes above 12,000 feet.
By the Numbers
- Age of range~35 million years
- Weminuche Wilderness500,000 acres
- Nearby fourteeners7 within 20 mi
- Forest established1905
- Alpine tundra begins~12,000 ft
- Colorado Trail486 mi total
Ecosystems & Wildlife
From river valley to alpine tundra
Alpine Tundra
Above approximately 12,000 feet, the forest gives way to alpine tundra -- a fragile, wind-scoured landscape of low grasses, cushion plants, and tiny wildflowers that bloom in a brief window between snowmelt and the first September frosts. This ecosystem is among the most delicate in the Rockies; the plants grow only fractions of an inch per year, and a single footstep off-trail can leave a mark visible for decades.
Subalpine Forest
Between roughly 9,000 and 12,000 feet, dense stands of Engelmann spruce and subalpine fir cover the mountainsides. These forests are home to black bear, mountain lion, and the elusive pine marten. In autumn, groves of quaking aspen punctuate the dark conifers with brilliant gold, creating the fall color displays that draw photographers from across the country.
Large Mammals
The San Juans support healthy populations of elk, mule deer, and bighorn sheep. Black bears are common in the lower valleys and oak brush, while mountain lions range across all elevations. In the highest terrain, white-tailed ptarmigan -- Colorado's only year-round alpine bird -- blend into the rocks and snow, nearly invisible until they move.
Mining History
The San Juans were the site of some of Colorado's richest gold and silver strikes, beginning in the 1860s and continuing through the 1990s. Historic mining districts dot the range, with ghost towns, abandoned mills, and old wagon roads scattered across the high country. Towns like Silverton, Ouray, and Telluride all began as mining camps before reinventing themselves as mountain communities.
Recreation
A lifetime of exploration
The San Juans offer four-season recreation on a scale that is difficult to match anywhere in the lower 48 states. In summer, hundreds of miles of trail lead to alpine lakes, wildflower meadows, and summit ridges. The Colorado Trail, the Continental Divide Trail, and countless local paths weave through the range. Peak-bagging, backpacking, fly-fishing, and rock climbing are all within reach of a single basecamp.
In winter, Purgatory Resort provides lift-served skiing and snowboarding, while the backcountry offers cross-country skiing, snowshoeing, and ice climbing. The Million Dollar Highway and San Juan Skyway scenic loop remain open year-round, offering dramatic drives through snow-covered passes. Jeep roads and the Alpine Loop Byway open in summer for those who want to explore the most remote corners of the range by vehicle.
Your door to the San Juans
Stay at the base of Purgatory Resort, surrounded by the peaks, trails, and wilderness of the San Juan Mountains.