These criminals were the worst of the worst! For this list, we’ll be looking at the most notorious criminals to have been imprisoned inside Alcatraz, based on their reputations and crimes. Our countdown includes Mickey Cohen, Whitey Bulger, Al Capone, and more! Have you ever visited the historic prison? What did you think? Let us know in the comments below!

10. Roy Gardner
Known as the "King of the Escape Artists," Roy Gardner was a notorious bank robber and train robber. He attempted several daring escapes from other prisons before being transferred to Alcatraz, where his escape attempts were finally thwarted.

9. Arthur "Doc" Barker
A member of the infamous Barker-Karpis gang, Arthur "Doc" Barker was involved in numerous robberies and kidnappings. His criminal activities led to a life sentence at Alcatraz, where he attempted an escape in 1939 but was ultimately shot and killed.

8. George "Machine Gun" Kelly
One of the most notorious gangsters of the 1930s, George Kelly Barnes, better known as "Machine Gun" Kelly, was known for his involvement in bootlegging, kidnapping, and bank robbery. He was sent to Alcatraz in 1934 and remained there until his transfer in 1951.

7. Robert Stroud ("The Birdman of Alcatraz")
Robert Stroud, known as the "Birdman of Alcatraz," was initially convicted of murder. Although he was not allowed to keep birds during his time at Alcatraz, Stroud became famous for his extensive knowledge of ornithology and his written works on bird diseases.

6. James "Whitey" Bulger
Boston mobster James "Whitey" Bulger was known for his violent reign over the Winter Hill Gang. After being implicated in numerous murders and criminal activities, Bulger spent time in Alcatraz during the 1950s before becoming one of America's most wanted fugitives.

5. Mickey Cohen
A notorious figure in organized crime, Mickey Cohen was a key player in the Los Angeles underworld. His involvement in various illegal activities, including gambling and racketeering, led to his imprisonment at Alcatraz in the 1960s.