The "mason dixon line" is a common metaphor used to describe a separation, usually directional (north or south). It can also be used to describe other separations such as above and below the waist.
Geographically speaking, one could say: "The mason dixon line separates the yanks (people who stereotype everyone and think the nation should have voted for Kerry or Frankenstein, which ever you prefer) from those who are more refined and choose not to cry about such trivialities as who is the president (he is more symbolic than political anyways).
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