The Cook County medical examiner's office says three women died at the scene. A fourth woman was later pronounced dead at a Chicago hospital early Sunday. She was identified as 21-year-old Leshia Nelson.
The names of the other women were not immediately available.
Chicago police spokesman Hector Alfaro says the car was speeding when it hit the beam of a Chicago Transit Authority train track just before midnight and then struck a light pole. Chicago fire officials say the vehicle crashed with enough force that it split in two.
Police are investigating the crash.