The Cache la Poudre River (French for "powder store"), begins in Poudre Lake just east of the Continental Divide at Milner Pass in Rocky Mountain National Park. The water flows north into Roosevelt National Forest, picking up numerous creeks as it progresses. After 30 miles, the current veers around to the east and begins coursing through a deep canyon. Near this turning point lies the Big South trailhead, ...

starting at the junction of the river and State Hwy 14. For the next 40 miles it charges downhill through narrow gorges and wide, smooth-surface glens, all the while closely bordered by a narrow, windy HWY 14. The river flows from the canyon through the city of Fort Collins and on to the eastern plains from there. It is fishable along most of it's course.