TRIVIAL PURSUITS: Why was the Mason-Dixon line drawn?

However, the original purpose of the Mason-Dixon line was not to distinguish the North from the South during the U.S. Civil War.

It was established to settle an 18th century boundary dispute between the Penn family in Pennsylvania and the Calvert family in Maryland. In 1760, the families agreed to have two English astronomers and surveyors settle the dispute.                                                         

From 1763 to 1767, Charles Mason and Jeremiah Dixon established the boundary.