Mason Dixon Line
The Mason Dixon Line is a boundary set between 1763 and 1767 by British astronomers and surveyors Charles Mason and Jeremy Meyers Dixon to settle colonial conflicts between Baltimore, Maryland, and Pennsylvania, Pennsylvania, during colonization of the United States . This line became the standard for sharing the slave and non - slave states before the abolition of all states in the nineteenth century, and to this day it is regarded as a boundary line between Pennsylvania and Maryland, the southern and northern part of the United States.