The FBI has now released portraits of the unknown victims, drawn by Little in his cell, in the hope of receiving more information about them.
Many of the women appear to have individual details that may help identify them.
For instance, one teenage victim from Miami is sporting a blue headband while a victim from Texas has purple hair.
FBI agents said Little was able to evade justice for several decades by targeting marginalised and vulnerable women involved in prostitution or drugs whose disappearances attracted scant attention.
Little, a former boxer, would stun his victims with a sharp blow before strangling them.
The absence of knife or gun wounds led police to mistakenly attribute many deaths to overdoses or accidents.
A large number of the murders were committed in the Seventies and early Eighties, before police began using DNA profiling.
Samuel Little murdered more than 90 people over three decades. Now he’s drawing them from a California prison cell from memory. https://t.co/XjaRV7VeAv
Little was already serving a life sentence for murdering three women in 2014 when he agreed to speak to investigators in another cold case in exchange for a prison transfer.
He then began confessing to dozens of murders committed between 1970 and 2005.
By November 2018, he had admitted 90 killings, but the scale of his crimes rose further when he recalled three more in December.
Little has made portraits of 16 of his victims who remain unknown.
The FBI said he had a vivid memory for detail when it came to the women's faces and how he had killed them, but was less reliable on the dates of crimes.
Little reportedly told officers that he was a good drawer and promised last year to produce portraits of his victims.
He used a combination of chalk, pastel pencils and water colours to capture the faces of 16 of the women.
