Overview
Mount Oso is the hardest of Colorado's 200 highest peaks to reach. The climb itself is only Class 2+, but it sits far from any road. The closest start is the Hunchback Pass trailhead, which needs a 4WD, and the backpack to Rock Lake is a full day for most people. It can also be climbed from Moon Lake. This is deep in the Weminuche Wilderness, so plan a multi-day backpack and follow wilderness rules on camping, fires and group size.
From a camp below Rock Lake you follow the trail past the lake to a pass above Half Moon Lake, leave the trail, and cross a broad ridge into the big tundra basin east of Oso. A wide talus slope leads to the southeast ridge, which you follow north-northwest past a narrow notch, over loose boulders and then flat, clinking plates of rock, to the summit.
The round trip is about 25.3 miles with 7,100 feet of gain from the trailhead. The Rock Lake camp is about 10 miles in; from there the climb is about 5.5 miles and 2,300 feet round trip, plus about 300 feet regained on the way back. Peters Peak and other 13ers are close to Rock Lake. Very strong hikers have done Oso in one long day from the trailhead, about 22 miles and over 6,000 feet.
Plan of the day
From camp, leave by 6:30 a.m.
Be on the southeast ridge by 11 a.m.
Steep, loose boulders low on the southeast ridge.
Moderate. Leave the trail where it turns south toward Half Moon Lake, and pick the talus slope that leads onto the southeast ridge.
Rock Creek, Rock Lake and the ponds above it. Filter it.
Getting to the trailhead
Hunchback Pass
This trailhead needs a high-clearance 4WD, and plan on as long as 2.5 hours of driving from Silverton. From the northeast end of Silverton, take County Road 2 up the Animas about 4.2 miles to Howardsville. Turn right up Cunningham Gulch, then take the left fork onto the Stony Pass road. It climbs steeply over the pass and down the far side. You will ford Pole Creek, then turn right at a fork and ford the Rio Grande. Both fords are harder early in the summer. Then follow the Beartown road about 4 slow, rough miles past the old Beartown site and up a rocky, rutted stretch. The Hunchback Pass trailhead is about half a mile below Kite Lake, at roughly 11,800 feet, with limited parking.
You can also reach this area from Creede or Lake City by driving to Rio Grande Reservoir, but the road west of the reservoir has very rough sections. There is some camping near the trailhead and near the old Beartown site.
Base towns and camping for this climb
Coming from out of state? See Lodging & Camping for how free camping works, what is closed this year and where to stay.
Before you go
Check these the week of your climb.
Official forecast
The National Weather Service forecast for the summit area, hour by hour. Look for thunderstorm chances and wind above treeline.
NWS point forecast →Directions to the trailhead
Hunchback Pass. Road conditions near the trailhead change after storms. Check your clearance and have a backup plan for a lower lot.
Get directions →Roads and highways
Closures, construction and winter conditions on the highways that get you there.
COtrip road conditions →Closures and fire rules
Trail closures, fire bans and other alerts from the Forest Service in Colorado. For the latest on your trailhead, call the local ranger district.
Forest Service alerts →Snow on the route?
From fall through early summer, any snow slope can slide. Check the avalanche forecast before you go.
Avalanche forecast →Cell signal
Most trailheads and many summits have little or no signal. Check coverage near the trailhead and carry a satellite messenger or beacon if you can.
FCC coverage map →