Tionda Bradley, who was 10 at the time she disappeared, and her sister Diamond, who was 3, were last seen July 6, 2001.
Their mother, Tracey Bradley, went to work early that morning. When she returned at 12:30 p.m. to the Lake Grove Village complex at East 35th Street and Lake Park Avenue in the Bronzeville neighborhood, the family's apartment was empty.
Bradley initially gave contradictory accounts of her whereabouts to police. She later said she did so because she feared a backlash from police for leaving the girls alone.
Tionda left a note saying the girls were visiting Doolittle School, about a block from their home. The family searched and finally called police around 6 p.m.
In one of the most extensive manhunts in recent Chicago police history, officers searched more than 5,000 abandoned buildings and interviewed more than 1,000 individuals, including most of the sex offenders living in the area.
Children at a playground said they saw the girls but also gave contradictory accounts.
The family and law enforcement officials still hold annual vigils to mark the girls' disappearance. Chicago police and the FBI say they are actively investigating the case.
-- by David Jackson and Gary Marx