The New Mexico State Penitentiary (also called Old Main) is the site of one of the worst prison riots in U.S. history. In February 1980, inmates took over the facility for 36 hours. While some prisoners simply tried to find a safe place to wait out the riot, others banded together to rampage through Old Main, torturing and murdering other inmates. A total of 33 prisoners are believed to have died during the riot and about 100 more were injured or suffering from drug overdoses.

On February 2nd 1980, a combination of overcrowding, mistreatment, poorly trained guards, and a system in which prisoners were forced to snitch on each other came to a head.

Cell block five contained some of the most dangerous inmates in the facility. A week earlier, these men were placed in an open dormitory, E2, while renovations were being made to cell block five. That is where the riot began.

Just after 1:00 a.m., a group of inmates jumped four guards.

They seized the correction officers’ keys, which gave them access to most of the prison. Guards had also failed to secure several doors that were supposed to be locked. Hundreds of prisoners were freed from their cells. They were able to break into the supposedly impenetrable control center and overtake Old Main.

Some prisoners headed straight for the infirmary to raid the pharmaceutical supplies. Others had a different destination in mind.

Cell block four housed a range of at-risk prisoners, including informants.

The rioters had keys to the block, but not to the individual cells. A group of men, sometimes referred to as an execution squad, used blowtorches liberated from the construction project on cell block five to access these cells. They tortured, abused, and murdered many of the men in the protective custody unit.

Negotiations began between several groups of prisoners and the officials outside the facility, which included the State Police and National Guard.

The prisoners had 12 guards as hostages.

During the riot, some inmates had broken pipes and started fires. Parts of Old Main were under a foot of water, while a fire in the gymnasium was spreading.

Prisoners began approaching the perimeter fence.

After 36 hours, the state and city police entered the facility and regained control of the prison.

The 12 guards all lived, although some had been brutalized and were badly hurt.

The number of prisoners killed is usually listed as 33, but some of them had been dismembered, making the final death toll uncertain.

Old Main closed in 1998 but you can sometimes take a tour. Limited numbers of visitors walk through the building, where hatchet marks are still visible on the floor.

The goal is to use funds from tours to turn Old Main into a museum. The theme of these tours is: "Respecting our Past to Create a Better Future," so it’s not a haunted prison tour. Visitors are subject to searches and must sign a waiver. Tours sell out quickly. Check the New Mexico Corrections Department website to see when one will be available. (At time of publication, ticket sales for 2016 appear to have ended.)

If you'd like to learn more about the riot, view this BBC documentary that includes interviews with both corrections officers and ex-inmates of Old Main. (It does contain some graphic descriptions of the violence.)

Do you remember the New Mexico prison riot? Would you want to tour Old Main?