By way of offering information,
donn
San Quentin is not a jail but a prison. Here, jails are local county lockups and a prison is ran by the state. A jail houses inmates who for the most part are awaiting trial or a hearing (such as a reduction of sentence for one who has already been convicted of breaking the law), or for one who has been sentenced for committing a misdemeanor. The max. sentence is usually 1 year and the population is for the most part not dangerous, although there is always someone around who is interested in establishing a more "respected reputation" by using physical force. Housing in different areas of a jail is therefore extremely important to keep the more vicious from preying on the weaker. For a some years, I headed a program that offered mental health services to the Fresno County jail population, including those from Atascadero State Hospital (for mentally ill criminals) awaiting a hearing to determine re-establishment of sanity.
On the other hand, a prison houses those who have been convicted of a felony and have been sentenced. The population is therefore much more dangerous, especially with the numerous gang affiliates who end up in prison. As much as possible, members of different gangs are housed in different prisons to prevent altercations. Unlike inmates, prisoners usually have already established their hierarchy (sometimes from a county jail occurrence prior to transfer). Violence is of a more deadly nature and is always simmering below the surface.
(A lesser known movie which I feel depicts prison life well is "Felon" starring Stephen Dorff and Val Kilmer. Another is "An Innocent Man" starring Tom Selleck).
San Quentin State Prison is located approx. 15 or 20 miles across the Golden Gate Bridge, north of San Francisco. It also is the site of Death Row for male inmates in California and still has a gas chamber, although lethal injection was the method most recently used. In California, capital punishment has had a roller coaster ride history of being temporally halted only to be reinstated, and executions are presently again halted due to a 2019 moratorium by the present governor. According to Wikipedia, the last execution was in 2006 and there are presently over 700 male inmates on Death Row and over 20 female who are on Death Row in the Central California Women's Facility in Chowchilla (about 20 miles west of me, as the crow flies).
OG