Why was US' most secure prison Alcatraz closed in 1963?

The Alcatraz prison, which US President Donald Trump has said will be reopened, was closed in 1963 because it was too expensive to continue operating. Billed the most secure US prison, Alcatraz was nearly three times more costly to operate than any other federal prison. No successful escapes were ever officially recorded from Alcatraz due to its island location.