Sumas, Washington (Wikipedia) Sumas (SOO-mas) is a city in Whatcom County, Washington, United States. It had a population of 1,583 as of the 2020 census. Sumas is located adjacent to the Canada–U.S. border and borders the city of Abbotsford, British Columbia. The Sumas–Huntingdon port of entry at the north end of State Route 9 operates 24 hours a day. Sumas shares Nooksack Valley School District with the cities of Nooksack and Everson. It is the northernmost settlement on Washington State Route 9.