I know he’s in prison but which one?
Manson is serving his time Corcoran State Prison since 1989 (transferred there from San Quentin), which was built on what used to be Tulare Lake in Kings County. Manson was denied parole in 2012 and won't be eligible for parole again until 2027, when he's 93.
I met Charles Manson when I was allowed to sit in on a group therapy session as part of a tour at California Medical Facility Men's Prison where Manson was being held temporarily for a short term while I was a college student. . . chilling experience. He just sat there and stared at people.