Services provided by inmates are defined by 18 USC 4125(a) and include preservation and maintenance of grounds and facilities; construction, repair and demolition of buildings; road repair; custodial services; and transportation of debris to recycling centers. Only minimum security inmates are available under the Army's civilian inmate labor program. Army personnel do not provide security supervision of inmate work details, but do monitor and account for inmate presence or absence in an assigned work area. from the link given by GUEST above

I'm of two minds about this. Obviously it takes away jobs from the people, but at the same time, it saves money and teaches skills and work habits and it makes sense to me if rehabilitation, not punishment, is the main rationale for incarceration.

At the Oregon Correctional School outside Salem, there are vast fields where the inmates used to plant and harvest many of their own food. All of it in-house, none of it sold on the market. The practice was discontinued when the local unions raised the issue. The fields now lie empty.