Rising in Wyoming’s Wind River Mountains, and fed by snowmelt from the Uintas of Utah, the Green River is a critical waterway in the American West. Its course not around but through the Uintas, by way of Lodore Canyon and Split Mountain in modern-day Dinosaur National Monument, perplexed the explorer John Wesley Powell. The distinctive descending song of the tiny canyon wren (Catherpes mexicanus) is often heard along its banks.