History's Mysteries - Chain Gangs (History Channel Documentary)
Narrated by David Ackroyd
A chain gang is a group of prisoners chained together to perform menial or physically challenging work as a form of punishment. Such punishment might include repairing buildings, building roads, or clearing land.
This system existed primarily in the Southern United States, and by 1955 had been phased out nationwide, with Georgia the last state to abandon the practice.
Chain gangs were reintroduced by a few states during the "get tough on crime" 1990s, with Alabama being the first state to revive them in 1995.
The experiment ended after about one year in all states except Arizona, where in Maricopa County under then-Sheriff Joe Arpaio, inmates could still volunteer for a chain gang to earn credit toward a high school diploma or avoid disciplinary lockdowns for rule infractions
Current (2019) Maricopa County Sheriff Paul Penzone has said that he would scale back the use of inmate chain gangs.
~ Description courtesy of Wikipedia, edited and updated for clarity