The Powder River is a significant waterway located in the western United States, primarily flowing through the states of Wyoming and Montana. It is approximately 125 miles long and is known for its scenic landscapes and historical importance, particularly during the westward expansion of the United States. The river is a tributary of the Yellowstone River, contributing to the region's ecosystem. It is also notable for its role in the Powder River Basin, an area rich in natural resources, including coal and natural gas, which has been a focal point for energy development and environmental discussions.