On March 22nd, 2014 at 10:37 am, the deadliest landslide in US history engulfed the community around Steelhead Haven, about 4 miles east of Oso, Washington.
A portion of tree-covered hillside above the North Fork Stillaguamish River gave way, sending masses of mud and timber flowing across the river, through the Steelhead Haven neighborhood and onto State Route 530. The debris field covered an area of approximately 1 square mile (or 2.5 square kilometers), and was up to 70 feet (or 21 meters) deep in places.
The mudslide killed 42 people in the residential area and one in a car travelling on the highway, and left 4 with serious injuries. A memorial at the site includes 43 cedar trees planted in honor of each of the lives lost, and Highway 530 was officially renamed as Oso Slide Memorial Highway.
The cause of the mudslide is believed to be soil instability caused by water saturation after heavy rainfall.