there were several gambling ships that served the los angeles area in the 1930's.
Typically the ships would be moored 3 miles off shore, and patrons would arrive by water taxi service out of long beach and san pedro.
The Juanita Water taxi alongside a gambling ship
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LAPL
As GW mentioned, the Rex was probably the most famous of these illicit cruisers
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LAPL
there was also the Mount Baker
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LAPL
The Tango
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LAPL
The Johanna Smith
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LAPL
the Lux, also known as the Bunker Hill....(
that's where i would have gone for my prohibition gamblin' and hootch fix!)
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LAPL
sometimes the long arm of the law would catch up with these operations
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LAPL
Source:
LAPL
and every so often, the ships would be subject to organized union issues
Source:
LAPL