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Sourdough Trail

Arapaho and Roosevelt National Forests, Colorado · 6 min read

Distance
15 mi
Elevation Gain
1,800 ft
Difficulty
moderate
Route Type
Point-To-Point
Best Season
June through October
Dog Friendly
Yes
Difficulty Score
6 / 10
Trailhead Amenities
Restroom
None
Parking
Free
Cell Service
No Signal
Water
Nearby
Camping
Dispersed
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Conditions, regulations, and fees change frequently. Verify with the local ranger district before your trip. Full disclaimer

At a Glance

  • 15-mile subalpine traverse through Roosevelt National Forest with far fewer crowds than Brainard Lake
  • Multiple access points allow flexible shorter segments
  • Popular for trail running, mountain biking, and cross-country skiing in winter
  • Forested terrain with periodic meadow openings and filtered peak views

Overview

The Sourdough Trail runs 15 miles through the subalpine forest of Roosevelt National Forest between Rainbow Lakes Campground to the south and Brainard Lake Road to the north. The trail sits at elevations between 9,000 and 10,500 feet, staying mostly in the trees and rolling through a landscape of Engelmann spruce, subalpine fir, and occasional meadow clearings. It is not a trail with dramatic alpine lake destinations or sweeping summit views - instead, it offers a sustained, low-key forest traverse that is notably less crowded than the Brainard Lake Recreation Area trails that draw the majority of the region's visitors.

The trail is open to hikers, trail runners, and mountain bikers, making it one of the more versatile routes in the area. In winter, sections of the Sourdough Trail are used for cross-country skiing and snowshoeing. The lack of a single dramatic destination also means the Sourdough is a good option when Brainard Lake parking is full: it's close, accessible from multiple points, and free.

At 15 miles point-to-point, the full trail is a significant undertaking. The elevation gain is spread across the full distance and is not particularly steep in any single section, which is why it's classified as moderate despite the length. Shorter out-and-back segments are a common alternative for those without a car shuttle.

Dogs are allowed on leash throughout. No permit or fee is required at most access points.

The Route

South trailhead (Rainbow Lakes Campground, ~10,000 ft). The trail begins at or near Rainbow Lakes Campground off CR 116, north of Nederland. This section starts through open terrain in a burn area, with good views to the east and filtered views of the peaks to the west. The trail enters denser forest within the first mile.

Southern section (miles 0 to 6). The trail traverses the forest, crossing several small drainages. The terrain is rolling, with modest climbs and descents. This section is the rockiest part of the trail and the most technical for mountain bikers. Several social trails branch off the main route; follow signage and the main path.

Middle section (miles 6 to 10). The trail passes through more continuous forest with periodic meadow openings. A few small stream crossings can be muddy in early season. This section is less distinct from a scenery standpoint but offers the quietest hiking on the full route - most day hikers from either end don't reach this zone.

Northern section (miles 10 to 15). The trail approaches the Brainard Lake Road corridor, gaining the most elevation in this segment as it climbs toward the higher terrain around the recreation area. The northern terminus connects near Camp Dick and the Brainard Lake Road access.

Access points: The trail has multiple intermediate access points off CR 94N (the road north of Ward toward Brainard Lake Road). These allow hikers and bikers to cut the trail into shorter segments without a full shuttle.

Permits and Fees

No permit or fee is required at the Rainbow Lakes Campground or most Sourdough Trail access points. Dispersed camping along the trail is permitted under Roosevelt National Forest regulations; camp at least 200 feet from water sources and trails, pack out all waste.

If your Sourdough hike connects into the Brainard Lake Recreation Area at the north end, the day-use fee ($15 per vehicle, as of 2026) applies there. The America the Beautiful pass covers fees at most standard federal recreation sites, though Brainard Lake's specific area fee is separate.

See our national forest camping permit guide for general guidance on dispersed camping and reservation systems.

When to Hike

June through October covers the full season. The lower-elevation access points near Rainbow Lakes Campground are typically accessible by early June, earlier than the higher Brainard Lake trailheads. The full trail can be snowy in late October and early November.

June and early July are great for the Sourdough if the higher Indian Peaks trails are still snow-covered. The subalpine forest keeps the trail cooler and largely snow-free earlier than the open alpine terrain above.

Winter: Sections of the Sourdough Trail are used for cross-country skiing and snowshoeing when snow conditions allow. The forest cover makes it more sheltered than open alpine routes. Check trail conditions before winter travel.

Afternoon thunderstorms: The trail stays mostly in the forest, offering some shelter (though not safety) from lightning. Still, plan your route timing to be back at the trailhead before afternoon storms build in July and August.

What to Bring

Water: Small streams and drainages cross the trail; carry a filter. Many hikers bring 2 liters and filter from streams for longer segments. Individual needs vary with pace, temperature, and segment length.

Navigation: The trail has multiple junctions and access points. Download an offline map through Gaia GPS or similar before leaving cell service. The USFS Arapaho-Roosevelt Motor Vehicle Use Map and trail maps are available from the Boulder Ranger District.

Layers: The subalpine zone at 9,000 to 10,500 feet can be cool even in summer, particularly in the morning and after afternoon showers. Carry a wind layer.

Bug protection: June and early July can bring significant mosquito activity near the wetter sections of the trail. DEET or picaridin-based repellent is worth having.

Bear awareness: Black bears are present in this forest. Review our bear canister guide for food storage requirements and recommendations if camping along the trail. Practice Leave No Trace principles throughout.

Trailhead Access

South trailhead (Rainbow Lakes Campground): From Nederland, take CO-72 north (Peak-to-Peak Highway) about 5 miles to CR 116. Turn left (west) on CR 116 and follow it approximately 5 miles to Rainbow Lakes Campground. The road is unpaved and can be rough in wet conditions. No fee at Rainbow Lakes trailhead access.

North access (Brainard Lake Road area): From Ward, take Brainard Lake Road west. Access points for the northern section of the Sourdough Trail are along CR 94N. Check with the Boulder Ranger District for current trailhead signing and parking.

From Boulder, the Rainbow Lakes south trailhead is about 30 miles and 45 to 50 minutes. From Denver, plan on about an hour and 15 minutes. For those based in the Nederland area exploring Arapaho and Roosevelt National Forests, the Sourdough Trail is one of the most accessible long-distance routes that doesn't require the Brainard Lake day-use fee.

Trailhead Parking

Multiple access points between Rainbow Lakes Campground (south end) and Brainard Lake Road (north end). Car shuttle recommended for point-to-point. No fee at most access points.

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Frequently Asked Questions

Do you need a shuttle to hike the Sourdough Trail?
For the full 15-mile point-to-point route, a car shuttle is strongly recommended. Leave one vehicle at the Rainbow Lakes Campground trailhead and drive the other to the Brainard Lake Road access point near the Camp Dick area. Alternatively, you can hike shorter out-and-back segments from either end without a shuttle. The trail can also be accessed at several intermediate points along CR 94N.
Is the Sourdough Trail open to mountain bikes?
Yes. The Sourdough Trail is one of the few multi-use trails in the Brainard Lake corridor open to mountain bikes. It is popular with Front Range mountain bikers looking for a sustained subalpine ride. Trail conditions vary by section; the southern segment near Rainbow Lakes tends to be rockier and more technical, while the northern section is smoother. Hikers and bikers share the trail and should be courteous at intersections.
Can you do sections of the Sourdough Trail as a day hike without a car shuttle?
Yes. The southern trailhead near Rainbow Lakes Campground and the northern access point near Brainard Lake Road can each serve as out-and-back starting points. A 6 to 8 mile out-and-back from either end covers the most scenic sections of the trail without requiring a vehicle shuttle. Most day hikers use the Rainbow Lakes Campground access for the southern section.