Associate Warden to Paul J. Madigan from April 1959,[1] Blackwell served as warden of Alcatraz at its most difficult time from 1961 to 1963, when it was facing closure as a decaying prison and financing problems and at the time of the June 1962 escape.

At that time, he was on vacation in Lake Berryessa in Napa County, California, and he didn't believe the men could have survived the waters and made it to shore.

Blackwell was considered to have been the least strict warden of Alcatraz, perhaps in part due to him having been a heavy drinker and smoker, nicknamed "Gypsy" and known as "Blackie" to his friends.

He had earlier served as Associate Warden of Lewisburg Federal Penitentiary.

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