The Cook County Medical Examiner identified two of the victims as 26-year-old Jaquira Brown of the 6400-block of South Wood Street and 22-year-old Lanae Dinnett Riley of the 1800-block of South Paulina.
Brown's sister, 20-year-old Jaunitra Holloman, is in critical condition.
Brown and Holloman's brother, Mooka G, said the crash happened when someone tried to rob his sisters. Police have not confirmed this information.
Relatives said Brown and Holloman were out celebrating a friend's birthday before the accident occurred.
A neighbor created a memorial to the victims later Thursday morning by placing roses and candles on the ground near the scene.
"It's sad. It's sad. First of all, I don't want to think why it happened," he said, thinking of how devastated the victims' families must be.
Emergency crews responded around 3:15 a.m. to a report of a crash near West 143rd Street and Harrison Avenue.
Police a driver lost control of a BMW as it approached a four-way stop. There were five people inside the car - a male driver and four women, one of whom may have been his girlfriend. Investigators said the BMW struck several parked vehicles and at least one of the victims was ejected.
The identities of the other two women killed in the crash have not been released. The male driver and fourth female passenger were taken in critical condition to Advocate Christ Medical Center for treatment.
The impact of the crash left Octavio Camacho's car totaled. He told ABC7 Eyewitness News he heard one of the officers who responded to the crash encourage a young woman to keep breathing.
"I could see two or three of them, right by that red car. That's where you saw the most. And then, you know, you don't know what to do. You just freeze there, you know? You want to help them, but you know you can't really do much," Camacho said.
Firefighters had to extinguish a small fire before investigators could start piecing together what led to the crash. Police said they don't think weather played a role in the wreck.
"We think alcohol is involved. Obviously, with the extensive damage to the cars - the parked cars - probably excessive speed. That's why we have the Accident Reconstruction Team out here to fill in those blanks," said Chief Doug Hoglund, Posen Police Department.
The investigation is ongoing.