Although the active search for victims ended in April, workers have been screening debris and watching for the body of Molly Kristine "Kris" Regelbrugge, 44.
Her husband, Navy Cmdr. John Regelbrugge III, also was killed in the slide that hit their home. His body was one of the 42 recovered earlier.
Her body was found about 8 a.m. in an area where personal items believed to belong to the Regelbrugge family had been located previously, the sheriff's office said Tuesday.
The area on the west side of the slide site, south of Highway 530, needed to be secured for workers but they expected to complete the recovery by the end of Tuesday.
The Snohomish County medical examiner will confirm the identification.
"I'm humbled and honored that we are able return Kris to her family," Sheriff Ty Trenary said. "I'm also extremely grateful to the communities of Oso, Darrington and Arlington who stood beside us these past four months in our efforts to recover all of the missing victims."
The discovery came on the same day that a team of scientists released the results of a report into the causes of the deadly mudslide.
The report says intense rainfall likely played a major role in triggering the slide, but that many other factors also contributed, such as previous landslide activity that also weakened the slope that collapsed.
The team says the slide, the deadliest in U.S. history, occurred in two major stages. A fast-moving mudflow remobilized a 2006 slide, bringing down old slide deposits across the valley. Another slide followed a few minutes later.
The report makes several broad recommendations that include doing an examination of landslide risks and communicating the information to the public.