Have you ever been to a “lunch counter”?
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Maybe because my wife and I prefer back roads to superhighways (as long as there is no timeline), I see them all the time.
And you are right, they are one-offs, little places in forgotten towns.
Last 2, outside of Storrs CT, and in Oakland MD.
When travelling with my father, I would go into little bars in towns like that - where they’d only sell soda to a neatly dressed girl with her dad, even if the girl was 30!