This girl 
once mentioned to me that I was the only person she knew to ever mention the Mason-Dixon Line in casual conversation. I’d said something like “Going south of the Mason-Dixon line is sometimes like going back in time a hundred years.”
However, as long as they’re trying to revive whites-only proms in Georgia, I think the term — and my remark — still apply. For starters, the young lady and her very charming accordion-playing gentleman friend in the picture above wouldn’t be allowed to go.
(According to the article, one of the rationales behind the whites-only prom was a desire to “avoid problems arising from interracial dating”. As an expert in this field, the only problems arising from interracial dating all stem from the bigotry of others. That’s the problem with wearing pillowcases on your heads, people — they’re cutting off the oxygen to your brains.)
[Thanks to Smittie, who pointed me to cls.blog, for the link.]