'He's Building a Concentration Camp': Fears Grow as Images Emerge of Offshore Prison at Gitmo.

Slavery is independent of prison ownership. You’re referring to involuntary servitude versus the abolished chattel slavery. Privatization is an additional layer of systemic oppression.

Private prisons may or may not partake in indentured servitude. In addition to participating in the constitutionally protected slavery, they have far more systemic problems than public prisons. The goal is to spend as little as possible to meet minimum legal requirements in order to maximize profit (it’s a business, after all). Many of these for-profit prisons are infrequently or improperly evaluated, leading to far worse conditions than governmentally run prisons. There have also been countless cases of people being denied parole to maintain minimum headcount.

Modern private prisons first emerged in 1984 when the Corrections Corporation of America (CCA), now known as CoreCivic, was awarded a contract to take over operation of a jail in Hamilton County, Tennessee. See comment below for link to the origins of private prisons.