The Skagit River divides the park into the north and south districts; it lies outside the park boundaries, but some of the creeks and streams that supply it originate within the park; the Baker River is the largest of these tributaries. The Skagit River is the largest river that flows into Puget Sound to the west, and the dams located in Ross Lake National Recreation Area and impounding other lakes adjacent to the park supply nearly 90 percent of the electricity used in Seattle. Other important rivers that originate in the park include the Chilliwack, Nooksack and the Stehekin rivers.