Police know who killed her. They know when she died. They know where she died. And they even know what she was doing before her life ended: talking on a pay phone, being told her divorce was finalized.

But 46 years after the young woman was murdered in the Maryland woods by one of the most prolific serial killers in American history, she remains unidentified.

Now, it’s suspected that she may have been from Salem or Springfield — a clue offered up by the killer himself.

Samuel Little, who has allegedly confessed to murdering 90 women across the country between 1970 and 2005, recently told a Prince George’s County, Md., police corporal, Bernard Nelson, that the victim he killed some 20 miles west of Washington, D.C., had ties to Massachusetts.

“It was chilling talking to him because he talked as if he was just hanging out with friends having a few beers,’’ Nelson said of his interview with Little.

The woman’s death “was nothing to him. He gets energized describing how he killed his victims. You are dealing with a monster in every sense of the word.’’

Little told Nelson that “on the day that [Little] killed her, she was happy.’’

“She was on the pay phone and had learned her divorce was finalized. She was happy to hear that,’’ Nelson said. “She didn’t have much time to celebrate.’’

Little, who was sentenced to three life terms for murdering three women in California, is now in a Texas jail, where he confessed his ruthless rampage to Texas Ranger James Holland and FBI agents from the Violent Criminal Apprehension Program.

Law enforcement officials have determined that Little’s confessions to 34 murders are valid and are working to document more, officials said.

Nelson and his Prince George’s County colleagues were among the numerous investigators from various jurisdictions who have interviewed Little in an effort to solve cold cases.

During their interview, Little provided a detailed account of where he met the woman and how they came to know each other. And then — in graphic, remorseless detail — he described how she fought to stay alive in the summer of 1972, Nelson said.

Little told police she was a 19-year-old white woman, with “dirty blonde’’ or “dishwater blonde’’ hair, about 5 feet 2 inches to 5 feet 6 inches tall. She told Little she was either from Springfield or Salem; he said he couldn’t remember which one.

She also told him she was going through a divorce, and she may have told him that she was the mother of a child. Little also recalled what she was wearing: a black skort (shorts that look like a skirt).

But Little could not remember her name.

Nelson’s career has included interviewing serial killer Jason T. Scott, known as the “mother daughter killer’’ for killing five people, including a Prince George’s woman and her 20-year-old daughter in 2009. Scott is serving an 85-year state sentence and a 100-year federal sentence.

“Jason Scott was just weird,’’ Nelson said. “Samuel Little is a monster.’’

During the interview, Little told police that he had met the woman when she was working as a prostitute out of a Washington bus station where Nelson had parked the car he lived in.

After three days of interactions, Little convinced the woman to travel the country with him. The two were driving through Laurel, Md., when the woman asked to have consensual sex in the back seat of the car. They pulled into a wooded area, Little told Nelson.

“He climbed into the back seat of the car when he started to choke her. She told him she was too young to die and pleaded for mercy,’’ Nelson said.

“He kept choking her, and he thought he had killed her. But she came to and got out of the car and tried to stagger away. He forced her to the ground and strangled her.’’

“She just ran into the wrong person,’’ Little told Nelson.

Little said that after the Maryland murder, he drove to Boston, which may have been the original plan between the two.

Little was arrested on a theft charge in Boston on June 7, 1972, which was also his birthday.

“He knew his way around Boston,’’ Nelson said of Little.

(The FBI has not publicly linked Little to any unsolved homicides in the Boston area.)

The woman’s remains were found by a hunter in December 1972 in a wooded area off Route 197 and the Baltimore-Washington Parkway.

Police tried to identify the woman in the 1970s, without success. Four years ago, police collected biological samples still available to them and sent them to the University of North Texas and its Center for Human Identification.

A DNA profile was created, but Nelson said that since then, investigators have not been able to match it to any family members. Little’s confession has provided new information about the woman and has sparked a renewed effort to find out who she was.

Nelson said investigators checked out the nine women who were reported missing in Massachusetts prior to the woman’s death in the summer of 1972. But none of them are the woman in the woods, he said.

He said the woman may never have been reported missing back in the 1970s, possibly because relatives shunned her after she turned to prostitution. During his career, Nelson said, he has often come across women who were never reported missing.

State Police are now digging through Massachusetts divorce records from 1972, in hopes of finding a possible name.

Nelson said that if someone is located, a DNA match would be used to confirm her identity.

Investigators are urging people to think about a high school classmate or college classmate who disappeared around 1972.

Nelson said he and his law enforcement colleagues remain dedicated to learning who the victim was.

Anyone with information is asked to call 301-772-4925. Callers wishing to remain anonymous may call Crime Solvers at 1-866-411-TIPS (8477), or go online at www.pgcrimesolvers.com.

John R. Ellement can be reached at ellement@globe.com. Follow him on Twitter @JREbosglobe.