Sumas, WA (Washington) Houses and Residents. Total population: 1,348 (Urban population: 0, Rural population: 965 (all nonfarm)) Houses: 405 (343 occupied: 322 owner occupied, 178 renter occupied) Housing density: 290 houses/condos per square mile. Median price asked for vacant for-sale houses and condos in 2015 in this county: $857,481.