Mason-Dixon Line

The Mason–Dixon Line (or "Mason and Dixon's Line") is a demarcation line between four U.S. states, forming part of the borders of Pennsylvania, Maryland, Delaware, and West Virginia (then part of Virginia). It was surveyed between 1763 and 1767 by Charles Mason and Jeremiah Dixon in the resolution of a border dispute between British colonies in Colonial America. Popular speech, especially since the Missouri compromise of 1820 (apparently the first official usage of the term "Mason's and Dixon's Line"), uses the Mason-Dixon line symbolically as a cultural boundary between the Northern United States and the Southern United States (Dixie).
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Noun
1. the boundary between Maryland and Pennsylvania; symbolic dividing line between North and South before the Civil War
(synonym) Mason and Dixon Line, Mason and Dixon's Line
(hypernym) state line, state boundary