Mason-Dixon Line

In the USA, the boundary line between Maryland and Pennsylvania (latitude 39° 43' 26.3" N), named after Charles Mason (1730-1787) and Jeremiah Dixon (died 1777), English astronomers and surveyors who surveyed it 1763-67. It is popularly seen as dividing the North from the South.

The two colonies had argued for almost a century and even fought some armed skirmishes over the boundary. In 1760, the two agreed to allow Mason and Dixon to delineate the line.