Litchfield Penitentiary houses a Maximum Security facility on its property. It has been where the show has taken place in Season Six following the Season Five riot. It is often referred to by inmates as "Max". Maximum Security is down the hill from the camp, as seen in "Empathy Is a Boner Killer". The SHU building is attached to the Max building. This section of the prison is reserved for the inmates of minimum security who have acted violently, smuggled or used drugs, or other serious offenses; as well as, presumably, inmates who were sent straight there due to the nature of their crimes.
Life in Max is first shown in "Piece of Shit".
As of the end of season 6, Max holds 635 inmates. The combined number of inmates from AdSeg, B-Block, C-Block, and D-Block is far less than 635, so there must be another part of Max that hasn't been shown yet. This is supported by the fact that we see inmates in cells with bars rather than doors, separate from the four blocks, during Nicky's first stay in Max, and also by the fact that Nicky said she had 5 roommates during her first stay but the cells shown in season 6 only hold 1-2 inmates. According to Nicky, during her first stay in Max, she had five roommates, one of which put her baby through the spin cycle.
There are a few cell blocks in which inmates may be assigned, based on their perceived personality and threat level. There's been four blocks for the entire prison.
A-Block is the Administrative Segregation, where inmates are sent right after reaching the prison. It's described as "the lighter side of SHU", as those cells have extremely small size, only having a larger window, a possibility to make calls, and also having a short recreational time in another room. However, time in A-Block is very short as inmates are getting interrogated, and then later being sent to the other blocks. A-Block inmates wear orange uniforms.
AdSeg cells can also hold two inmates at once (a cot is brought in for the second inmate) if there's too many new transferred prisoners.
B-Block is a cell block for inmates who need high-level protection in the prison, such as women who are mentally or physically disabled, transgender, or elderly. B-Block is also known for having the best conditions in the whole prison, as they get fresh fruit, pudding, a safer and calmer environment, and also a possibility to watch TV. B-Block inmates wear pink uniforms, and are often envied by the inmates from the other cell blocks. Florida is said to be the only safe place in the prison, as B-Block doesn't take a part in the fight between C-Block and D-Block. Some known residents are: Suzanne Warren, Frieda Berlin, Galina Reznikov, Lorna Morello Muccio, Taslitz, Tiffany Doggett (thanks to a deal with Linda Ferguson), and Sophia Burset (formerly; released).
C-Block is a cell block formerly runned by Carol Denning. Inmates from C-Block get better jobs, and a higher standard of living than inmates from D-Block, which was a cause of frequent clashes between these two blocks. However, after the death of Carol and Barbara, inmates from C-Block seem to bury a hatchet with D-Block. C-Block's inmates are also known for their cruel and violent behavior. They wear navy coloured uniforms.
Some known residents are: Carol Denning (formerly; deceased), Alex Vause (formerly; transfered to the prison in Ohio), Madison Murphy (formerly; transfered to the prison in Missouri), Galina Reznikov (formerly; transfered to B-Block), Alana Dwight, Piper Chapman (formerly; released), Gloria Mendoza (formerly; transfered to D-Block), and Blanca Flores (formerly; transfered to an ICE Detention Centre).
D-Block is a cell block formerly runned by Barbara Denning. Most inmates from this block have the worst offenses, such as murder. Many inmates from this block are also drug addicts. D-Block inmates have much lower conditions than those from C-Block, which was a cause of frequent clashes between those two blocks. However, after the death of Carol and Barbara, inmates from D-Block seem to bury a hatchet with C-Block. They wear beige uniforms.
Some known residents are: Barbara Denning (formerly; deceased), Dayanara Diaz, Aleida Diaz, Marisol Gonzales, Maria Ruiz, Gloria Mendoza (after being transferred from C-Block; formerly; released), Cindy Hayes (formerly; released), Tasha Jefferson, Dominga Duarte (formerly; deceased), Annalisa Damiva, Juanita Vazquez, Nicky Nichols, Lorna Morello Muccio (formerly; transferred to B-Block), Adeola, and Irene Cabrera.
The following inmates are those who have been previously sent to maximum security: