Through DNA testing, detectives identified the baby's mother as Melissa Jean Allen Avila, police said in a Thursday news release.
It is unclear whether Avila, who police accused of murder, has obtained an attorney. CNN has made efforts to reach Avila.
Avila made an initial appearance in court Wednesday and was released on her own recognizance through an agreement between the prosecution and the defense, according to City News Service. She was previously being held on a bond of $1.1 million, police said.
CNN has left a message with the Riverside County District Attorney's Office requesting information about the case.
The newborn had been found deceased in a dumpster in Riverside on October 13, 1987, by a man rummaging for recyclables, police said in the release.
Homicide investigators were unable to identify a suspect and the case went unsolved for nearly 40 years. In 2020, the department's new homicide cold case unit reopened the case.
Police said they worked with Othram, a DNA testing company, with funding from Season of Justice, a nonprofit that provides financial assistance for investigative agencies and families to help solve cold cases with "advanced DNA analysis solutions and forensic genealogy."
In November 2021, Othram was able to get DNA from evidence in the case and build a profile for the baby, according to its website. The police agency's forensics genetic genealogy team then developed new leads that led to potential relatives.
"Othram assisted with investigators' reference testing efforts using (a method of testing that) allows investigators to infer kinship in closely and distantly related individuals," the company said.
Avila was taken into custody in Shelby, North Carolina, which is about 45 miles west of Charlotte.
Avila was 19 at the time of the baby's death. There was no evidence the baby's father had any link to the case, police said.
"Thanks to the persistent efforts of our investigators and partners, this victim now has an identity, bringing resolution to the case," Riverside Police Chief Larry Gonzalez said. "We will remain dedicated to seeking justice for homicide victims and ensuring their families find closure."
Avila's next hearing is scheduled for September 9, according to jail records.
The-CNN-Wire & 2024 Cable News Network, Inc., a Warner Bros. Discovery Company. All rights reserved.