What was the spanish dungeons used for in alcatraz?

The Spanish dungeons in Alcatraz, which date back to the mid-19th century, were originally built as military fortifications. They were later repurposed for use as a prison, particularly for holding prisoners in harsh conditions. The dungeons served to isolate and discipline inmates, reflecting the strict and punitive approach of the military and later the federal prison system. Their dark, cramped environment exemplified the severe treatment of prisoners during that era.