- Granite Falls is a city in Snohomish County, Washington, United States. It is located between the Pilchuck and Stillaguamish rivers in the western foothills of the Cascade Range, northeast of Lake Stevens and Marysville. The city is named for a waterfall north of downtown on the Stillaguamish River, also accessible via the Mountain Loop Highway. As of the 2020 census, Granite Falls had a population of 4,450.