All the victims were black and were found in or near South Los Angeles. Police believe some of the women were prostitutes.
Seven women and a man were killed by the same handgun in a three-year period starting August 1985. The women had been sexually assaulted and their bodies were often dumped in the same alley in South Los Angeles.
The Los Angeles City Council on Wednesday approved the reward first proposed by City Councilman Bernard Parks, who as police chief in 2001 ordered the department to look into a backlog of unsolved cases.
Alicia Monique Alexander was the last known victim in the first round of killings. Porter Alexander last saw his youngest daughter one evening in September 1988 as the 18-year-old ran out for what was supposed to be a quick trip to the store.
"I said make sure you go to the store and come back. She says, 'OK,"' Porter Alexander said. "She left, and that was the last time I saw my baby."
Four days later, police knocked at the front door of the family home. They'd found her body in a nearby alley with a gunshot wound in the chest.
A 13-year hiatus followed Alexander's death, police said, and investigators retired or moved on to other cases.
"What accounted for that gap, we still don't know," police Capt. Denis Cremins said at a news conference Wednesday. "We try not to engage in conjecture."
The hiatus ended in March 2002, when 14-year-old Princess Berthomieux was found beaten and strangled in an alley in the city of Inglewood. DNA samples linked her to the suspect in the earlier murders.
Another killing came in 2003, and the most recent homicide was in January 2007 when the body of Janecia Peters, 25, was found shot and covered in a garbage bag.
The length of time between the killings prompted the LA Weekly newspaper, which first reported the case, to dub the killer the "Grim Sleeper."
Though police have a DNA sample, only one physical description of the killer exists, taken from a victim who survived a 1988 attack. She said the assailant was a black man in his 30s driving an orange Ford Pinto.
"But that's one person's account who was traumatized," Cremins said.
Investigators are poring through prison and jail records to screen prisoners with a violent history who were locked up during the break in the killings. Authorities also hope to search DNA databases to see if there are any possible matches to the killer's family members.
Parts of Los Angeles suffered extreme violence in the 1980s and '90s and many young women turned to the streets to fund newfound addictions to crack cocaine and other drugs.
Alexander said police initially seemed to drag their heels when it came to investigating his daughter's death. He said he did not believe his daughter was a prostitute but that she did have a drug problem.