State troopers responded to the scene, on Cook Road east of Collins Road, at about 5:45 p.m. after receiving a report of a serious crash.
The motorcyclist, Christopher T. Mask, 48, and his passenger, Kathleen L. Mask, 55, both of Sedro-Woolley, were taken to Skagit Valley Hospital. Kathleen Mask died from her injuries at the hospital.
A preliminary investigation found that a 2001 Honda Accord driven by John R. Albrecht, 76, of Sedro-Woolley was heading east on Cook Road.
At the same time, the Masks' 2012 Harley-Davidson motorcycle was stopped in the eastbound lane of Cook Road, waiting to make a left turn.
The Honda failed to stop and crashed into the rear of the motorcycle, the State Patrol reported.
Albrecht was not injured. He was booked into Skagit County Jail for investigation of vehicular homicide and vehicular assault.
Alcohol or drugs were believed to be a factor in the crash.