From Lost for Words by John Humphrys (Hodder)
A gauche young man from rural Mississippi won a scholarship to Harvard. On his first day there he approached a couple of cocky young New England socialites.
“Hey, y’all, where’s the library at?”
They sniggered among themselves and one replied haughtily, “At Harvard we prefer not to end our sentences with a preposition.”
The young redneck thought for a moment and siad, “Okay, where’s the library at, asshole?”