Starting as a mere trickle on the east side of the Continental Divide, inside Rocky Mountain National Park, the Big Thompson flows from Forest Canyon Pass near the top of Trail Ridge Road through Forest Canyon. As small drainages offer additional snowmelt, the Big Thompson picks up volume, turning into one of Colorado’s finest streams.

The Big Thompson becomes fishable at Moraine Park in Rocky Mountain National Park, about six miles downstream of its headwaters. It’s there at Moraine Park, where the river splits into numerous braids and channels, that fisherman encounter the river’s first public access. Trails leading up and down the river from that point will lead you to great flyfishing experiences.

Moraine is a wide-open area, but the Big Thompson’s banks are lined with willows. It’s typical small stream conditions, and the river is filled with, you guessed it, brook, brown, and cutthroat trout in the 6- to 12-inch range. They’ll readily take a variety of general attractor flies.