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.

The Lower Mainland is a geographic and cultural region of the mainland coast of British Columbia that generally comprises the regional districts of Metro Vancouver and the Fraser Valley. Home to approximately 3.05 million people as of the 2021 Canadian census, the Lower Mainland contains sixteen of the province's 30 most populous municipalities and approximately 60% of the province's total population.