The Nooksack River is a river in western Whatcom County of the northwestern U.S. state of Washington, draining extensive valley systems within the North Cascades around Mount Shuksan, Mount Baker and the Twin Sisters, and a portion of Fraser Lowland south of the Canada–United States border.

Whatcom County is a county located in the northwestern corner of the U.S. state of Washington, bordered by the Lower Mainland of British Columbia to the north, Okanogan County to the east, Skagit County to the south, San Juan County across Rosario Strait to the southwest, and the Strait of Georgia to the west. Its county seat and largest population center is the coastal city of Bellingham, comprising the Bellingham, WA Metropolitan Statistical Area, and as of the 2020 census, the county's population was 226,847.