Several major rivers originate in passes and meadows within the park. The Skagit River, a major stream that runs into Puget Sound in the state of Washington, originates at the west side of Allison Pass and flows northwest alongside Highway 3 until it reaches its confluence with the Sumallo River at Sumallo Grove, where it turns southwest and exits the park into Skagit Valley Provincial Park. Just under half of the Sumallo River's course is within the park; it enters the park at West Gate, which is near the small town of Sunshine Valley. It too follows Highway 3 within the park, following it southeast to its confluence with the Skagit. The lower reaches of the small Skaist River, often mistakenly called Skaist Creek, are within the park. The Skaist flows into the Skagit directly across the valley from Silverdaisy Mountain.