State troopers responded to the scene, at Old Highway 99 and Mima Acres Drive, at about 7 p.m. Saturday after receiving a report of a crash.
Arriving at the scene, they found that a woman had sustained very serious injuries after crashing her 2002 Toyota pickup through a wooden fence.
The victim, later identified as Colleen L. Stuart, 50, of Rochester, was rushed to Harborview Medical Center in Seattle. She died there a few hours later.
An investigation found that Stuart had been driving west on Old Highway 99 approaching Mima Acres Road when her pickup veered off the roadway to the right, went through the fence and came to rest in the field.
The cause of the accident remains under investigation.
No one else was involved in the crash.