Birding · Fall Colors · River/Creek · Views · Wildflowers · Wildlife
From the Peak To Peak Highway, take the exit for the CU Alpine Research Center and park at the trailhead on the left. An outhouse is available at the parking lot.
This singletrack trail ascends to the Brainard Lake road, which splits the southern and northern halves of the Sourdough Trail. The southern half of Sourdough is less rugged than the northern half, and travels through splendid forest that rarely opens up enough for a vista.
This first two miles are a constant ascent on fairly loose rocks and will keep you on your toes. The grade isn't too steep, but there's not much of a break until you get to a pretty bridge over a stream crossing at 2.5 miles.
The trail becomes smoother at this point, but keeps climbing for a while with occasional views east through the trees. After about 3.5 miles, the trail becomes flatter and much faster to the end.
To return to the trailhead, either run back on the trail or along the Peak To Peak Highway.
The trail is open year-round is snow covered from fall to spring.