One was left in a park. Another was in a waterway near a motorsports complex. The youngest, 14, was left on a bedroom floor of a vacant house, discovered only when a potential homebuyer explored the place.
After roughly three decades, Portland police believe they now know who killed them.
Homer Lee Jackson, 55, of Portland, was arrested Thursday after a grand jury indicted him on counts of aggravated murder, police announced Friday.
Police credited their cold case unit, assigned to investigate long-unsolved crimes, with connecting forensic evidence and other investigative information in the four killings to Jackson.
"The main thread that kind of is woven through this story is the fact that they were all victims of sex trafficking,
and he would patronize services of these women and women like them, and he targeted them for that reason," Portland police Detective Meredith Hopper told CNN affiliate KPTV
Jackson pleaded not guilty to the charges Monday.
All four victims, African-American females in their teens or 20s, were involved in prostitution, police said. Each died of asphyxiation, either by drowning or strangulation, Portland police Sgt. Peter Simpson said.
• Essie Jackson, 23, a mother of one. Her body was found near the edge of north Portland's Overlook Park in March 1983. She is not related to the man accused of killing her.
• Tonja Harry, 19. She was found dead in the Columbia Slough, between a golf course and Portland International Raceway, in July 1983.
• Angela Anderson, 14. Her body was found in the vacant house in September 1983; police said they believe she had been dead for two weeks.
• Latagna Watts, 29, a mother of three. She was found dead in a grassy area near a pedestrian bridge over Interstate 5 in March 1987.
The cold-case unit began investigating the cases when the unit debuted in 2004. Last year, detectives and forensic investigators began using new technology to test physical evidence, KPTV reported.
Police declined to detail the evidence, saying they needed to withhold information because the investigation isn't finished.
Police said that the victims' relatives weren't ready to speak about Jackson's arrest, CNN affiliate KATU
One of Jackson's neighbors, Beverly Jones, told KPTV that he "didn't seem like he was running" from anybody.
"He ... stayed to himself a lot," Jones, who lives in the same apartment complex as Jackson, told KPTV. "Sometimes we had barbecues and we would come down and speak, and stuff like that. Other than that, he seemed like a good person."
Hopper said Jackson spoke with detectives upon his arrest and seemed "relieved."
"A lot of times we get questioned (by suspects), like, 'Why am I here? What is this about?' And (Jackson) never really did," Hopper told KPTV.