A driver headed north on Highway 101 crashed south of Petaluma late Monday night and was found dead in his car, reported the CHP.
Other drivers called 911 at 11:38 p.m. saying a silver sedan had run off of the highway near the Redwood Sanitary Landfill.
Officers found the Ford Fiesta in a field, with little collision damage, said the CHP.
A man behind the wheel was slumped over in his seat, unresponsive.
Officers had to break a window to get to the man. Attempts to revive him failed.
The cause of death appeared to be unrelated to the car crash and remained under investigation.
The driver's name was withheld until his family was told.