advertising had convinced most people that nothing made outside of
Milwaukee was
worth drinking, . . .

One word on the label had something to do with that. If you shipped your
beer out of state, there was an extra tax levied on it. This tax was known
as a "premium". So, beer shipped from Wisconsin was marked "Premium" beer.
Joe Six-Pack thought this meant it had to be extra good. Doh.

Sorry, but that sounds like an Urban Legend. Can you please cite a
source?

vince norris