Finally! A question I'm qualified to answer.
Well, I've trained in 8 out of the 31 prisons in California, and 2 out of
in the federal prison system and I've even gotten in a few workouts in the Joint down in Venezuela.
As mentioned, Calif pens no longer have any legit iron. Some of the fire-camps in Cali do have a little iron but very little. The Federal system still has weights but not at the level they once did. The MCC Metropolitan Correctional Center down in Dade County, Florida has a nice set up.
I'm pretty sure the pens in Pennsylvania still have excellent weight rooms for the boys.
I'd reccomend not trying to gain any mass while working out in the prisons in Venezuela. They had a few 1960's Universal machines but the pins were always being turning into shanks so there was never a pin to put in the weight stack.
Now back until 1995 San Quentin (and pretty much all Cali pens) had a kick ass set-up. Outdoor weights, indoor gym, Olympic iron, contest every few months... Everybody got huge.
Attica! Attica! Attica!