Biohazard Cleanup Near West Sumas Sumas, WA

Sumas is a city in Whatcom County, Washington, sitting directly on the Canada–U.S. border, where it adjoins 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, and Sumas is the northernmost settlement on that highway.

Because of surveying limits when the border was drawn, the boundary west of the Cascades lies slightly north of the 49th parallel — the offset reaches about three city blocks at Sumas, making it the northernmost incorporated place in the contiguous United States.

The name Sumas comes from a Cowichan word meaning "land without trees" or "big flat opening"; the area was Nooksack Indian homeland for millennia before the first permanent settler, Robert Johnson, arrived in 1872.

Originally called Sumas City, the town was officially incorporated on June 18, 1891, and a post office named Sumas has operated since 1897.

Sumas grew as a railroad hub and a supply point for the Mount Baker Gold Rush, and gold mining has continued in the area, including at the Lone Jack mine.

In the early 20th century Sumas was known for a large rodeo, the Sumas Roundup.

The 2020 census counted 1,583 people in Sumas, living in 568 households, and the city is young by Washington standards, with a median age of 32.3 years.

Sumas has grown quickly in recent decades, rising from 960 people in 2000 to 1,307 in 2010 and 1,583 in 2020.

The city sits in a broad floodplain draining toward the Fraser River, and on November 15, 2021, catastrophic flooding damaged roughly 85 percent of the homes in Sumas and forced hundreds of rescues; the city was hit by flooding again in December 2025.