State prison officials on Wednesday moved the last 36 inmates out of a Stateville Correctional Center “roundhouse” — a complex that a Chicago watchdog group dubbed “not fit for human habitation.”

The maximum-security F House at Stateville in Crest Hill — which housed 348 male inmates — is officially closed, the Illinois Department of Corrections said. No other prison in the U.S. has kept roundhouses, in which cells circle a watchtower in the middle. The F House was intended for inmates who posed a threat to staff or other inmates.

Gov. Bruce Rauner in October penned an op-ed in the Sun-Times about his plans to reform criminal justice in the state, calling the F House one of the state’s oldest and most costly prison housing units. He also announced then that a closed prison in Murphysboro would be reopened and repurposed as a Life Skills and Re-Entry Facility, a minimum security facility with a focus on preparing offenders for transitioning back to public life.

Inside a "roundhouse" at Stateville Correctional Center in 1957. Sun-Times File Photo.

Inside a “roundhouse” at Stateville Correctional Center in 1957. | Sun-Times file photo

Rauner’s decision upset members of the American Federation of State, County and Municipal Employees Local 1866, whose members work at the F House, and complained they weren’t given enough notice.

But the John Howard Association — a prison watchdog group — said the outdated roundhouse design “magnified the already distressing auditory and visually chaotic experience prison frequently inflicts.”

The Illinois Corrections Department began transferring out offenders on Oct. 26. A total of 348 prisoners were transferred from the unit to other open beds throughout the department. The department said closing the unit will help them cut overtime costs by filling 60 vacant posts instead. It also allows the department to divert $10.3 million in maintenance costs into other housing units and programs.

Convicted murderer Richard Speck, with painting supplies, at Stateville in 1989. Sun-Times File Photo.

Convicted murderer Richard Speck, with painting supplies, at Stateville in 1989. | Sun-Times file photo

It’s not yet clear what the unit will be used for, but the department said it “recognizes its historical value” and plans to maintain the building.

It was built in 1922 and is the only “roundhouse” left in the U.S. The state says the layout is outdated and created safety and operational hazards for both the staff and offenders.

Even among prisons, F House had a brutal reputation.

Mass murderer Richard Speck worked as a maintenance worker in F House in the early 1990s.

And in 1990, a guard shot at a trio of prisoners he saw attacking two other gang members on the main floor of F House, allegedly for violating the rules of the Chicago street gang to which all five belonged.

Standing in the center tower 25 feet above the main floor, the guard saw the three inmates had machete-like “shanks.”

“Drop your weapons immediately,” he shouted.

They didn’t, and the guard fired his shotgun, killing two and wounding the third.

Stateville Correctional Center in 1966. Sun-Times File Photo.

Stateville Correctional Center in 1966. | Sun-Times file photo