Alcatraz was one of the few prisons in America at the time to have hot water for showers. This wasn't a compassionate decision, but was intended to keep the prisoners from becoming too used to cold water in case they did get out of the prison and try to swim off the island.
During filming, tourists were still allowed onto the island, and a new boatload would arrive every half-hour. They became so much of a distraction that the majority of filming was moved to night shoots.
Clint Eastwood once said of his character Frank Morris: "Morris was a reclusive-type guy. He had no education, but according to prison records, he had an I.Q. of 133. He could have been a success in life if he had channelled his pursuits a little differently."
Theatrical movie debut of Danny Glover, as one of the prison inmates. He's the inmate that Frank first encounters when delivering books (although his voice is dubbed).
Frank Morris' (Clint Eastwood's) disorientation after being released from solitary confinement is based on actual inmate behavior. One ex-convict, who served in Alcatraz, said of time in solitary, "You either came out a man, or something less."
Fritz Manes: Clint Eastwood's regular producing partner as a prison inmate. The appearance was one of seven that Manes has made in Eastwood's movies.