Longmont is located northeast of the county seat of Boulder, about 31 mi/49.9 km north-northwest of the Colorado state capitol in Denver. It is a home rule municipality in Boulder, Weld Counties in the U.S. state of Colorado.
It is an easy going community only 16 mi/25.8 km away from Boulder. One of the most popular sports in Boulder is free running. One great trail to run is Sourdough Trail. It is a 11.2 mi/18 km, out and back or a 12.6 mi/20.3 km, loop trail. It is a challenging singletrack with the best part of it being the signage.
The entire trail is marked with blue diamonds, ensuring that you stay on the trail all the time. The trail has an elevation of 9195 to 10200 ft/2803 to 3109 m, so be prepared for unpredictable weather. It ends at Brainard road. It is a paved road and when you reach the middle section and turn right and then go downhill, you intersect highway 72.
In order to get to the trailhead, you need to cross CO 116. The next 1.5 mi/2.4 km have a descending route and cross a small stream and the rocky section of the trail. After 2.4 mi/3.8 km, go down to a bridge, that crosses over a river. At 4.9 mi/7.8 km, start the descent, leading to the end of the trail.
At the next 5.6 mi/9 km, decide if you want to run on the paved road or go back where you came from.