Whatever part of the Mid-Atlantic you hail from, whether it be Maryland, Pennsylvania, West Virginia (originally part of Virginia), or even Delaware, you probably have at least some common knowledge about the existence of the Mason-Dixon Line. Most notably it has always served as an identifiable state-line border and has even helped to clarify regional divides in many other ways as well. But why was it even established in the first place and what was its intended purpose initially? In this Flashback Friday Feature, I’m sharing the true history behind how the now-famous Mason-Dixon Line came about.
The Mason–Dixon Line, alternately referred to as the Mason and Dixon Line or Mason’s and Dixon’s Line has been around since the late 18th century. Between the years of 1763 and 1767 astronomer Charles Mason and surveyor Jeremiah Dixon, who were both originally from England, were hired to survey a 233-mile (375-km) line along the parallel 39°43′ N. The goal was to better define the long-disputed regional boundaries and overlapping land grants involving both the Penns (proprietors of Pennsylvania) and the Calverts (proprietors of Maryland).
This ongoing dispute actually began more than a century before, starting in the year 1632. That was when King Charles I granted a charter to Cecilius Calvert, the second Lord Baltimore for the establishment of a colony north of Virginia to that point “which lieth under the Fortieth degree of north latitude” and westward to the source of the Potomac. Later on, in 1681, his son King Charles II, granted to William Penn the area between 43° N and a line extending westward from “a Circle drawne [sic] at twelve miles distance from New Castle…” to “the beginning of the fortieth degree….” The following year, Penn received a grant in the Delaware peninsula, which Lord Baltimore had already laid claim to.
The struggles and uncertainty surrounding land ownership lasted for quite a while. Then, in 1750 Lord Chancellor Hardwicke of Britain ruled that the southern boundary of Pennsylvania should be a line running westward from the point at which the line dividing the Delaware peninsula was tangential to a circle with a radius of 12 miles (19 km) from the center of Newcastle. That’s when the line constituting the Delaware tangent and the Newcastle arc was resurveyed in 1765 by Mason and Dixon, running the east-west line from the tangent point, at approximately 39°43′ N. Milestones, brought over from England, were set with every fifth stone in the eastern portion, bearing the arms of the Penn family on one side and the Baltimore arms on the other. The Mason-Dixon Line was officially completed in 1768 costing a total of $75,000. Later, in 1779, Pennsylvania and Virginia agreed to extend the line westward five degrees from the Delaware River—a line running north from that point to be the westward boundary of Pennsylvania.
Over the years, the Mason-Dixon Line eventually came to symbolize the unofficial divide between what were considered northern and southern states in the nation. This division grew even more prominent as a marking point during the Civil War era when tensions between the North and South were at an all-time high. Most notably, it eventually came to signify the division between free and slave states.
The Mason-Dixon Line has since come to mean many different things to many different people. Furthermore, it continues to stand out as both a regional and symbolic marker today just as it did so long ago.