Ottawa County police confirmed the three died after the car they were traveling in collided with a pickup truck in Park Township, about 35 miles southwest of Grand Rapids, Michigan.
The grandmother, identified as Patricia Rayner, 62, and the granddaughter, Madi McMaster, died at the scene.
Madi’s mother, 24-year-old Casey McMaster, was taken to Butterworth hospital and died later, said Erick Poshnick, a supervisor at the facility in Grand Rapids.
Police said Rayner was driving and went through a stop sign, colliding with the pickup.
The truck driver and two children with him had minor injuries.