I’ve been waiting for someone else to tell this old story, but since no one has, maybe it’s a northern plains thing . . .
City slicker moves to the country. Everywhere he goes, drivers are giving him the finger. He finally gets fed up with it one day and asks a coworker why the country bumpkins are always flipping him the bird. The coworker is confused a moment, then laughs.
Turns out the bumpkins were giving the new guy the customary wave with the index finger from the steering wheel, which the city slicker interpreted as an obscene gesture.