The woman dropped the phone around 12:45 p.m. at the 69th Street station, according to Chicago police and fire officials.
She climbed down to get it and was hit by an approaching northbound train, authorities said. She was pronounced dead at the scene.
She was identified Friday by the Cook County medical examiner as 37-year-old Felon Smith, of Chicago.
Smith's death shocked some commuters on Thursday.
"It is just crazy that you can take technology so far to the point that you risk your own life for something. It's just a piece of metal," said Marsean Spencer a CTA rider.
Lee McAllister said her friends told her what happened during the incident.
"It slipped and fell out of her hand, and she tried to retrieve it. She went on the tracks to get her phone, but she couldn't get back up from off the tracks, and the 'L' was coming," McAllister said. "The 'L' came, and it hit her. She couldn't get back up. She should just have left the phone down there. It ain't worth her losing her life."
McAllister said she has also dropped her cell phone on the tracks before.
"I just left it there," McAllister said. "I'm not going to take a chance on losing my life."
[Significant Delays] Service on the Red Line has resumed with trains making all regular stops. Service was disrupted due to a medical emergency on the tracks at 69th. More: https://t.co/I0nVwWAKZb— cta (@cta) June 27, 2019
Red Line service was temporarily suspended between 63rd and 95th, the CTA said. Service resumed about 3:00 p.m.
CTA officials said no CTA customer should ever go onto CTA rail tracks, whether to retrieve an item or assist a person.
If necessary, customers should press CTA's emergency call buttons, which are found at all CTA rail stations. This notifies the customer service assistant or security guard that there is a problem. Those employees are equipped with radios and have direct radio access to the CTA Control Center, which can stop a train or cut power within seconds.