[mey-suh
n-dik-suhn] 
| the boundary between Pennsylvania and Maryland, partly surveyed by Charles Mason and Jeremiah Dixon between 1763 and 1767, popularly considered before the end of slavery as a line of demarcation between free and slave states. |
| Ma·son-Dix·on Line (mā'sən-dĭk'sən) The boundary between Pennsylvania and Maryland, regarded as the division between free and slave states before the Civil War. It was established between 1763 and 1767 by the British surveyors Charles Mason (1730-1787) and Jeremiah Dixon (died 1777). |
A boundary line between Pennsylvania and Maryland, laid out by two English surveyors, Charles Mason and Jeremiah Dixon, in the 1760s. Before and during the Civil War, the line was symbolic of the division between slaveholding and free states. After the war, it remained symbolic of the division between states that required racial segregation and those that did not.
Part of the boundary between Pennsylvania and Maryland established by the English surveyors Charles Mason and Jeremiah Dixon in the 1760s. The line resolved disputes caused by unclear description of the boundaries in the Maryland and Pennsylvania charters.
Note: Though the line did not actually divide North and South, it became the symbolic division between free states and slave states. Today, it still stands for the boundary between northern and southern states.