The Mason Dixon
Line History What is the Mason Dixon Line Map Where is the Mason Dixon Line Located The Mason Dixon Line borders what Northern
and Southern States South North Mason Dixon States Maps
The Mason–Dixon Line (or "Mason and Dixon's Line") is a demarcation
line between four U.S. states, forming part of the borders of Pennsylvania, Maryland, Delaware, and West Virginia (then part
of Virginia). It was surveyed between 1763 and 1767 by Charles Mason and Jeremiah Dixon in the resolution of a border dispute
between British colonies in Colonial America. Popular speech, especially since the Missouri Compromise of 1820 (apparently the first official usage of the term "Mason's and Dixon's Line"),
uses the Mason-Dixon Line symbolically as a cultural boundary between the Northern United States and the Southern United States
|The original Mason-Dixon Line
|(Original Mason-Dixon Line Map)
The Mason-Dixon Line became symbolic of the division between the "free
states" and "slave states" from the Missouri Compromise until the end of the American Civil War. Pennsylvania abolished slavery
before the end of the American Revolution while Maryland, Delaware, Kentucky, and Missouri remained slave states until the
end of the war.
After the Civil War, the line continued to be considered a cultural
boundary. Some have viewed it continuing westward from Pennsylvania down the Ohio River
to the Mississippi River, and crossing the Mississippi to place
Arkansas, Louisiana and Texas south of the line. Debate whether border states such as Missouri, Kentucky, Maryland and West Virginia belong on the north or south side of this boundary line continues
to this day. However, a common assumption of the split between "northern" and "southern" U.S. lies between Virginia and West
Maryland and Pennsylvania both claimed the land between the 39th and 40th parallels according to the charters
granted to each colony. The 'Three Lower Counties' (Delaware) along Delaware Bay moved into the Penn sphere of settlement,
and later became the Delaware Colony, a satellite of Pennsylvania.
In 1732 the proprietary governor of Maryland, Charles
Calvert, 5th Baron Baltimore, signed an agreement with William Penn's sons which drew a line somewhere in between, and also
renounced the Calvert claim to Delaware. But later, Lord Baltimore claimed that the document he signed did not contain the terms he had agreed
to, and refused to put the agreement into effect. Beginning in the mid-1730s, violence erupted between settlers claiming various
loyalties to Maryland and Pennsylvania. The border conflict between Pennsylvania and Maryland would be known as Cresap's War.
The issue was unresolved until the Crown intervened in 1760, ordering Frederick Calvert, 6th Baron Baltimore
to accept the 1732 agreement. As part of the settlement, the Penns and Calverts commissioned the English team of Charles
Mason and Jeremiah Dixon to survey the newly established boundaries between the Province of Pennsylvania, the Province
of Maryland, Delaware Colony and parts of Colony and Old Dominion of Virginia.
After Pennsylvania abolished slavery in 1781, the western part of
this line and the Ohio River became a border between free and slave states, although Delaware remained a slave state.
Mason and Dixon's actual survey line began to the south of Philadelphia,
Pennsylvania, and extended from a benchmark east to the Delaware River and west to what was then the boundary with western
The surveyors also fixed the boundary between Delaware and Pennsylvania and the approximately north–south
portion of the boundary between Delaware and Maryland. Most of the Delaware–Pennsylvania boundary is a circular arc,
and the Delaware–Maryland boundary does not run truly north-south because it was intended to bisect the Delmarva Peninsula
rather than follow a meridian.
|Mason-Dixon Line History
|(Mason-Dixon Line Historical Marker)
The Maryland–Pennsylvania boundary is an east-west line with approximate mean latitude of 39°
43' 20" N (Datum WGS 84). In reality, the east-west Mason-Dixon Line is not a true line in the geometric sense, but is instead
a series of many adjoining lines, following a path between latitude 39° 43' 15" N and 39° 43' 23" N; a surveyor or mapper
might call it an approximate rhumb line. As such, the line approximates a segment of a small circle upon the surface of the
(also approximately) spherical Earth. An observer standing on such a line and viewing its path toward an unobstructed horizon,
would perceive it to bend away from his line of sight, an effect of the inequality between the amount of curvature to his
left and right. Among parallels of latitude, only the Equator is a great circle and would not exhibit this effect.
The surveyors also extended the boundary line to run or extend between
Pennsylvania and colonial western Virginia, which became West Virginia after the American Civil War, though this was contrary
to their original charter; this extension of the line was only confirmed later (see Yohogania County for details).
Mason–Dixon Line was marked by stones every mile and ”crownstones” every five miles, using stone shipped
from England. The Maryland side says (M) and the Delaware and Pennsylvania sides say (P). Crownstones include the two coats-of-arms.
Today, while a number of the original stones are missing or buried, many are still visible, resting on public land and protected
by iron cages.
Mason and Dixon confirmed earlier survey work which delineated Delaware's southern boundary from the Atlantic
Ocean to the ”Middle Point” stone (along what is today known as the Transpeninsular Line). They proceeded nearly
due north from this to the Pennsylvania border.
Later the line was marked in places by additional benchmarks and survey
markers. The lines have been resurveyed several times over the centuries without substantive changes to Mason and Dixon's
work. The stones may be a few to a few hundred feet east or west of the point Mason and Dixon originally specified; in any
event, the line drawn from stone to stone forms the legal boundary.
According to Dave Doyle at the National Geodetic Survey,
part of the National Oceanic and Atmospheric Administration, the common corner of Pennsylvania, Maryland, and Delaware, at
The Wedge is marked by Boundary Monument #87. The marker ”MDP Corner” dates from 1935 and is offset on purpose.
Doyle said the Maryland–Pennsylvania Mason–Dixon Line is
39° 43′ 19.92216″ N
and Boundary Monument #87 is on that
075° 47′ 18.93851″ W.
The line was established to end a boundary dispute between the British
colonies of Maryland and Pennsylvania/Delaware. Due to incorrect maps and confusing legal descriptions, the royal charters
of the three colonies overlapped. Maryland was granted the territory north of the Potomac River/Watkins Point up to the fortieth
parallel; Pennsylvania was granted land extending northward from a point "12 miles north of New Castle Towne," which is located
below the fortieth parallel. The most serious problem was that the Maryland claim would put Philadelphia, which became the
major city in Pennsylvania, within Maryland. A protracted legal dispute between the Calvert family, which controlled Maryland,
and the Penn family, which controlled Pennsylvania and the "Three Lower Counties" (Delaware), was ended by the 1750 ruling
that the boundary should be fixed as follows:
Between Pennsylvania and Maryland:
The parallel (latitude line) fifteen miles south of the
southernmost point in Philadelphia, measured to be at about 39° 43' N and agreed upon as the Maryland–Pennsylvania line.
Between Delaware and Maryland:
The existing east-west Transpeninsular Line from the Atlantic
Ocean to its mid-point to the Chesapeake Bay.
A Twelve Mile (radius) Circle around the city of New Castle,
A "Tangent Line" connecting the mid-point of the Transpeninsular Line to the western side of the
A "North Line" along the meridian (line of longitude) from the tangent point to the Maryland
Should any land within the Twelve-Mile Circle fall west of the North Line, it would remain
part of Delaware. (This was indeed the case, and this border is the "Arc Line.")
The disputants engaged an expert British team, astronomer Charles
Mason and surveyor Jeremiah Dixon, to survey what became known as the Mason–Dixon Line.
The Mason–Dixon line is comprised of four segments corresponding to the terms of the settlement: Tangent
Line, North Line, Arc Line, and 39° 43' N parallel. The most difficult task was fixing the Tangent Line, as they had to confirm
the accuracy of the Transpeninsular Line mid-point and the Twelve-Mile Circle, determine the tangent point along the circle,
then actually survey and monument the border. They then surveyed the North and Arc Lines. They performed this work between
1763 and 1767, and this actually left a small wedge of land in dispute between Delaware and Pennsylvania until 1921.
In April 1765, Mason and Dixon began their survey of the more
famous Maryland-Pennsylvania line. They were commissioned to run it for a distance of five degrees of longitude west from
the Delaware River, fixing the western boundary of Pennsylvania (see the entry for Yohogania County). However, in October
1767 at Dunkard Creek near Mount Morris, Pennsylvania, nearly 244 miles (392 km) west of the Delaware, a group of Native Americans
forced them to quit their progress. In 1784, surveyors David Rittenhouse and Andrew Ellicott and their crew completed the
survey of the Mason-Dixon Line to the southwest corner of Pennsylvania, five degrees from the Delaware River. Other surveyors
continued west to the Ohio River. The section of the line between the southwestern corner of Pennsylvania and the river is
the county line between Marshall and Wetzel counties, West Virginia. The boundary
between Pennsylvania and Maryland was resurveyed in 1849, then again in 1900.
The Missouri Compromise of 1820 created the political conditions which
made the Mason-Dixon Line important to the history of slavery. It was during the Congressional debates leading up
to the compromise that the term "Mason-Dixon line" was first used to designate the entire boundary between free states and
On November 14, 1963, during the bicentennial of the Mason–Dixon
Line, U.S. President John F. Kennedy opened a newly completed section of Interstate 95 where it crossed the Maryland-Delaware
border. It was his last public appearance; 8 days later in Dallas, Texas, he was assassinated. The Delaware Turnpike
and the Maryland portion of the new road were each later designated as the John F. Kennedy Memorial Highway.
(Sources and related reading below.)
Reading: A House Divided: Sectionalism and Civil War, 1848-1865 (The American Moment). Reviews: "The best short treatment of the sectional conflict and Civil War
available... Sewell convincingly demonstrates that the conflict was a revolutionary experience that fundamentally transformed
the Republic and its people, and left a racial heritage that still confronts America
today. The result is a poignant discussion of the central tragedy of American history and its legacy for the nation." -- William
E. Gienapp, Georgia Historical Quarterly.
"A provocative starting point for discussion, further study, and independent assessment." -- William H. Pease, History. "Sewell's
style is fast moving and very readable... An excellent volume summarizing the stormy period prior to the war as well as a
look at the military and home fronts." -- Civil War Book Exchange and Collector's Newsletter. Continued below…
traditional, and brief narrative of the period from the end of the Mexican War to the conclusion of the Civil War... Shows
the value of traditional political history which is too often ignored in our rush to reconstruct the social texture of society."
-- Thomas D. Morris, Civil War History. "Tailored for adoption in college courses. Students will find that the author has
a keen eye for vivid quotations, giving his prose welcome immediacy." -- Daniel W. Crofts, Journal of Southern History.
Reading: CAUSES OF THE CIVIL WAR: The Political, Cultural, Economic and Territorial
Disputes Between the North and South. Description: While South Carolina's
preemptive strike on Fort Sumter and Lincoln's subsequent call to arms started the Civil War, South Carolina's
secession and Lincoln's military actions were simply the last
in a chain of events stretching as far back as 1619. Increasing moral conflicts and political debates over slavery-exacerbated
by the inequities inherent between an established agricultural society and a growing industrial one-led to a fierce sectionalism
which manifested itself through cultural, economic, political and territorial disputes. Continued below...
This historical study reduces sectionalism to its most fundamental form, examining the underlying source
of this antagonistic climate. From protective tariffs to the expansionist agenda, it illustrates the ways in which the foremost
issues of the time influenced relations between the North and the South.
Reading: Manifest Destiny: American Expansion and the Empire of Right (Critical Issue Book). From Booklist:
In this concise essay, Stephanson explores the religious antecedents to America's
quest to control a continent and then an empire. He interprets the two competing definitions of destiny that sprang from the
Puritans' millenarian view toward the wilderness they settled (and natives they expelled). Here was the God-given chance to
redeem the Christian world, and that sense of a special world-historical role and opportunity has never deserted the American
national self-regard. But would that role be realized in an exemplary fashion, with America
a model for liberty, or through expansionist means to create what Jefferson called "the empire
of liberty"? Continued below…
bubbles in two periods Stephanson examines closely, the 1840s and 1890s. In those times, the journalists, intellectuals, and
presidents he quotes wrestled with America's purpose in fighting each decade's war, which added
territory and peoples that somehow had to be reconciled with the predestined future. …A sophisticated analysis of American
exceptionalism for ruminators on the country's purpose in the world.
Reading: Seizing Destiny: The Relentless Expansion of American Territory. From Publishers Weekly: In an admirable
and important addition to his distinguished oeuvre, Pulitzer Prize–winner Kluger (Ashes to Ashes, a history of the tobacco
wars) focuses on the darker side of America's rapid expansion westward. He begins with European settlement of the so-called
New World, explaining that Britain's successful
colonization depended not so much on conquest of or friendship with the Indians, but on encouraging emigration. Kluger then
fruitfully situates the American Revolution as part of the story of expansion: the Founding Fathers based their bid for independence
on assertions about the expanse of American virgin earth and after the war that very land became the new country's main economic
resource. Continued below...
The heart of
the book, not surprisingly, covers the 19th century, lingering in detail over such well-known episodes as the Louisiana Purchase
and William Seward's acquisition of Alaska. The final chapter looks at expansion in the 20th century. Kluger
provocatively suggests that, compared with western European powers, the United States
engaged in relatively little global colonization, because the closing of the western frontier sated America's expansionist hunger. Each chapter of this long, absorbing book is rewarding
as Kluger meets the high standard set by his earlier work. Includes 10 detailed maps.
Reading: The Impending
Crisis, 1848-1861 (Paperback), by David
M. Potter. Review: Professor Potter treats an incredibly complicated and misinterpreted time period
with unparalleled objectivity and insight. Potter masterfully explains the climatic events that led to Southern secession
– a greatly divided nation – and the Civil War: the social, political and ideological conflicts; culture;
American expansionism, sectionalism and popular sovereignty; economic and tariff systems; and slavery. In other words, Potter places under the microscope the root causes and origins of the Civil War.
He conveys the subjects in easy to understand language to edify the reader's understanding (it's
not like reading some dry old history book). Delving beyond
surface meanings and interpretations, this book analyzes not only the history, but the historiography of the time period as
well. Continued below…
rejects the historian's tendency to review the period with all the benefits of hindsight. He simply traces the events, allowing
the reader a step-by-step walk through time, the various views, and contemplates the interpretations of contemporaries and
other historians. Potter then moves forward with his analysis. The Impending Crisis is the absolute gold-standard of historical
writing… This simply is the book by which, not only other antebellum era books, but all history books should be judged.
Sources: Cope, Thomas D. 1949. Degrees along the west line,
the parallel between Maryland and Pennsylvania. Proceedings of the American Philosophical Society 93 (May 1949); Cummings,
Hubertis Maurice, 1962. The Mason and Dixon line, story for a bicentenary, 1763-1963. Commonwealth of Pennsylvania,
Dept. of Internal Affairs, Harrisburg, PA.; Danson, Edwin, 2001 Drawing the line : How Mason and Dixon surveyed the
most famous border in America. John Wiley & Sons, New York; Ecenbarger, William, 2000. Walkin' the line:
a journey from past to present along the Mason-Dixon. M. Evans, New York; Latrobe, John H. B. 1882. The
history of Mason and Dixon's line: contained in an address, delivered by John H. B. Latrobe of Maryland, before the Historical
society of Pennsylvania, November 8, 1854. G. Bower, Oakland, DE.; Mason, A.H. (ed.) Journal of Charles Mason [1728-1786]
and Jeremiah Dixon [1733-1779]. 1969. Memoirs of the American Philosophical Society vol. 76). American Philosophical
Society, Philadelphia; Nathan, Roger E. 2000. East of the Mason-Dixon Line: a history of the Delaware boundaries.
Delaware Heritage Press, Wilmington, DE.; Pynchon, Thomas. 1997. Mason & Dixon. Henry Holt, New York;
Sobel, Dava. 1996. Longitude: the true story of a lone genius who solved the greatest scientific problem of his
time. Walker & Co., New York; The Federal and State Constitutions Colonial Charters, and Other Organic Laws of the
States, Territories, and Colonies Now or Heretofore Forming the United States of America, Compiled and Edited Under the Act
of Congress of June 30, 1906 by Francis Newton Thorpe, Washington, DC : Government Printing Office, 1909.