When the prison first opened there were 52 guards but that grew as the number of inmates grew. It had a total staff of about155 including the guards,the warden and others. About 70 guards lived on the island. There are also about 300 civilians living on the island, which consisted mostly of the families of the guards, the warden and some of the staff.
52, according to Wikipedia.
When it was a working prison there were 56. None now of course.
Zero
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