Samuel Little, 79, sketched some of his victims’ faces to prove to the FBI, who filmed his confessions, that he killed them.
In one chilling clip, released on Sunday, Little confesses to drowning a woman in a river after picking her up in his car.
His murder spree took place between 1970 and 2005 and the majority of his victims were female.
Investigators have verified 50 of his confessions so far, the Mail Online reports.
The FBI has released Little’s video admissions and sketches on a website called Confessions of a Killer in a bid to discover the identity of his victims.
The killer has been serving a life sentence since 2014 for three murders and his confessions were filmed in prison during interviews with a Texas Ranger.
In another video he admitted to strangling a woman to death in North Little Rock, Arkansas, between 1992 and 1994.
He said she was too heavy to carry, so he dumped her body in a field.
Many of Little’s victims were originally thought to have died from overdoses or in accidents, the FBI said.
The FBI’s Violent Criminal Apprehension Program crime analyst Christie Palazzolo said: “For many years, Samuel Little believed he would not be caught because he thought no one was accounting for his victims.
“Even though he is already in prison, the FBI believes it is important to seek justice for each victim to close every case possible.”
Little confessed to his crimes in a bid to secure a prison transfer.
He has since been extradited to Texas over a murder in the state and is expected to die in jail.
Texas Ranger James Holland has spent more than 700 hours coaxing Little into confessing to more than 90 murders in 19 states.
His first interview took place in May last year, when Ranger Holland visited Little in California State Prison.