Charles Mason

Charles Mason (1728–1786) was an English astronomer and surveyor. He is best known for his work with fellow surveyor Jeremiah Dixon in establishing the boundary between Maryland and Pennsylvania in the United States. This boundary is famously known as the Mason and Dixon Line.123

Commissioned in 1763, Mason and Dixon surveyed this line along the parallel of latitude 39°43′17.6″ N. They worked for three years, marking milestones to define the disputed land grants of the Penn family and the Calverts. Their survey extended 233 miles and cost $75,000. Although they were prevented by hostile Native Americans from completing the final 36 miles, their work was ratified and has been accepted as the boundary ever since. The Mason-Dixon Line became a significant marker, often regarded as the dividing line between the Northern free states and the Southern slave states.23