Now, they want to know who the women are and what might have happened to them.
Detectives sought the public's help Thursday when they released images of about 160 women and asked anyone who recognized them to come forward.
"We certainly do not believe that we are so lucky, or so good, as to know all of his victims," Police Chief Charlie Beck said. "We need the public's help."
Lonnie Franklin Jr. has pleaded not guilty to the murders of 10 women from 1985 to 1988 and from 2002 to 2007. The apparent 14-year pause in the alleged crimes led to the nickname "Grim Sleeper," though detectives suspect Franklin could be involved in other deaths.
The photos and videos were found at Franklin's home and garage during a three-day search after his July arrest.
"Now that we know who he is and what type of activity he is involved in with women, we are very concerned for everyone in these photographs," Detective Dennis Kilcoyne said.
Police displayed the photographs for media and have made the images available online. By Thursday afternoon, the LAPD's website had slowed to a crawl after its Texas-based server was strained by a massive surge in people trying to click through to the pictures.
In almost every photo, the subject is smiling at the camera. Some women could have been naked but it's difficult to tell in the tightly cropped images. Others were photographed outside as part of a group photograph.
The women appear to be willing participants in what police said were sexually explicit images.
"It baffles me how he is so successful at getting women to do what he asks them to do," Kilcoyne said. "It's not like we have pictures of him holding a knife to someone's neck."
Detectives said the photos span decades and were taken on 35 mm film, Polaroids and digital cameras. Hairstyles range from 80s-style, big-bang blowouts to cornrow braids and a more contemporary flat-ironed look.
One picture, tagged No. 166, shows a woman in a nurse's outfit. Her name badge reads: Ms. D. Johnson - a name so common that investigators were never able to track her down.
A Polaroid, No. 141, has the hand-scrawled name Deborah B. Cleveland beneath it along with the date Sept. 18, 2001, and the notation "B.K.A. Chocolate." Photograph No. 172 shows a woman with rows of curlers in her hair.
The women range from young teens to 60-somethings. Except for two or three white women and a Latina, all the women are black. Some appear to be asleep.
Several known victims of the serial killer were said to be prostitutes. Detectives would not say if any of the women photographed might have been involved in the sex trade.
"We don't want to go down that road," Kilcoyne said. "For us to suggest the lifestyles or the situation that these women were in would defeat our plea to the public and to them to come forward."
Kilcoyne said investigators found the photographs throughout Franklin's house, including his garage and in his cars.
"Some were fallen behind items - cabinets and walls - others had been purposely secreted away," he said.
All of Franklin's alleged victims were killed within a few miles of his home, where neighbors knew him as a talented backyard mechanic.
Police also have said they suspect Franklin in the death of a man who may have discovered he was a killer. In addition, they are reviewing more than 30 other cold-case files to see if they can tie Franklin to other slayings.
Franklin was taken into custody last summer after his son was arrested and swabbed for DNA. Using a technique known as a familial DNA search, the sample came back as similar to evidence in the serial killings, ultimately leading police to Franklin.
In a different case, Huntington Beach detectives in March were inundated with hundreds of phone calls and e-mails after they released more than 100 photos discovered in serial killer Rodney Alcala's storage locker after his 1979 arrest.
More than 20 of the women were identified but none were victims.
The photos were released after Alcala was convicted of the murders of four women and a 12-year-old girl. He later was sentenced to death.
Photos of the women: http://bit.ly/erNS8Z