Oso, Wash., is a rural town along State Route 530 in Snohomish County, located approximately 60 miles north-northeast of Seattle, with a latitude of 48.27 north and longitude of 121.92 west. The rural area is in the foothills of the Cascade Mountains just north of the Stillaguamish River in northwestern Washington. A huge mudslide devastated a hillside east of the town on March 22, 2014, killing 44 people.
The 2010 official population of Oso was 180. The Oso city limits encompass 3.7 square miles. Oso is the Spanish word for bear, and the town is named after a ghost town in Texas of the same name. The closest large city to Oso is Everett, the county seat. The ZIP code is 98223 and the area code is 360, as of November 2014. Oso is located along the northern border of Snohomish County at an elevation of 207 feet above sea level. Snohomish County includes territory to the west of Oso down to sea level at Puget Sound.
The 2014 mudslide that occurred four miles east of Oso was the deadliest in U.S. history, as of November 2014. Several factors led to the disaster, including weeks of heavy rain, a smaller mudslide in the area in 2006, logging in the area that loosened up soil and erosion along the Stillaguamish River. County officials halted new construction in Oso for six months following the natural disaster.