The Mason Dixon Line

Mason Dixon Lores 75
Charles Mason and Jeremiah Dixon’s A Plan of the West Line… (Philadelphia, 1767)
Private Collection

The first time I saw the Mason Dixon Line it was hanging on a wall above a staircase.  It wasn’t what I expected.  Instead of dividing North from South it was dividing a first floor from a second floor.  A line can either divide or contain, and this dividing line was contained.  Captured.  In a rectangle, between the words “Province of Pennsylvania” and “Province of Maryland,” inside of another rectangle, inside of a frame, inside of a house.  “The Mason Dixon Line” as “Mason and Dixon’s Lines.”  Dividing.  Upstairs from downstairs.  Maryland from Pennsylvania.  North from South.  Slave from free.

18th Century English Surveyors Compass. Collection of the Wachovia Historical Society at Old Salem Museums and Gardens.

Jeremiah Mason and Charles Dixon would have been amazed to see their line thus captured, physically collected but symbolically charged.  To the two surveyors, “north” and “south” were nothing more than marks on their instruments.  Slavery, what their line would come to symbolize, existed on both side.  To Mason and Dixon, these ink lines, carefully measured and drawn between 1763 and 1767, were a means to an end, the resolution of a decades-old boundary dispute between Pennsylvania and Maryland.  Their manuscript map was merely the final requirement of their survey, after which Charles Mason could write “thus ends my restless progress in America.”[i]

Like all lines, this one is arbitrary.  It existed as an idea – the 40th parallel of latitude – in Mason and Dixon’s minds before they ever foot in America.  It existed fully drawn on the manuscript, a single line bisecting a rectangle, before the rest of the geography was drawn in.  There is no such thing as a straight line in nature.  So Mason and Dixon created one, bending the landscape to the will of the line.  Their ax-men opened a narrow vista in the forest.  Perfectly straight.  More than 230 miles across field and stream; seventy-two inches across paper on linen.  At every mile the surveyors placed a stone with the letters “P” and “M”; every five miles they placed a stone with the Arms of the Penn and Calvert families.  The line itself is an illusion.  A series of points.  Its “line-ness” only evident in the space between the markers.

Mason and Dixon Stones copy
Milestones and Crownstones. Individual images from The Mason Dixon Line Preservation Partnership.

To the people they encountered Mason and Dixon must have seemed like astrological augurers.  Every night they unpacked their instruments, went inside their portable observatory, read the stars, and emerged from the darkness to winnow the Pennsylvanians from the Marylanders.

Mason and Dixon Printed Map Cartouche Detail
Detail from the printed edition of Charles Mason and Jeremiah Dixon’s A Plan of the West Line… (Philadelphia, 1768). Library of Congress.

Only later did those same people and their children decide that they had actually be divided northerner from southerner, slave from free.  There is a saying: “southern by the grace of God”; according to Mason and Dixon one was southern by the alignment of the stars.

Mason Dixon Signatures
Detail of the Cartouche from Charles Mason and Jeremiah Dixon’s A Plan of the West Line… Private Collection.

Over time nature reclaimed the physical line: in the 1850s writers claimed that the vistas opened for Mason and Dixon by their axmen were just barely visible in the forest.[ii]  Some of the markers that Mason and Dixon set have been lost to the elements.  Even Mason and Dixon’s own signatures, affixed in acidic iron-gall ink below the cartouche, were slowly dissolving until conservation carried out by Colonial Williamsburg in 2004 fixed them in place.  As if to separate the permanence of geometry and geography from the impermanence of man, Mason and Dixon drew the rest of their manuscript in carbon black ink, a more stable and permanent medium.[iii]

Bugs Bunny and Yosemite Sam on the Mason Dixon Line
Yosemite Sam and Bugs Bunny at the Mason Dixon Line. Sold by Brunk Auctions in 2007

Paper disintegrates, ink disolves, but the Mason Dixon Line remains.  But where is the Mason Dixon line?  Never a society to let geography or history get in the way of a good symbol, the Mason Dixon Line – so precisely delineated on the physical landscape – has proven remarkably malleable on the popular landscape.  In the popular imagination the Mason Dixon Line was the boundary between the Confederate States and the United States; shocking news to Maryland and Delaware, neither of which seceded from the Union.  The geographical coincidence between the Mason Dixon Line of 1768 and the Missouri Compromise of 1820 required John H.B. Latrobe, a Marylander lecturing about the Line in 1854, to assure his audience that his remarks on the history of the Line “whose name has been oftener in men’s mouths during the last fifty years” would not touch upon the peculiar institution it had come to symbolize.[iv]

The Eastern Portion of the Mason Dixon Manuscript Map
Charles Mason and Jeremiah Dixon A Plan of the Boundary Lines… (Philadelphia, 1767)
Princeton University

In fact, the only thing divided by the Mason Dixon Line during the Civil War was the manuscript itself.  In 1864 Benjamin Chew mistook the manuscript of the eastern part of the line for a printed copy and gave it to a family friend.  In 1953 that error was realized when the eastern manuscript was given to Princeton University.  The western part of the line remained in the Chew family archives where it was only rediscovered in 1963.[v]

In 1982 the Chew family sold the western portion of the Mason Dixon manuscript map at Christies where it was purchased by Malcolm Forbes Jr.[vi]   When a reporter for Maine Antiques Digest asked if he would reunite the two parts of the manuscript at Princeton he responded, “I rather think I’ll ask Princeton to lend the Forbes Collection the rest of the map.”[vii]

In 2002 the Forbes family sold the manuscript at auction.[viii]

It is still a map divided.

It seems fitting that the Mason Dixon Line, the symbol of America’s great regional divide, is itself divided, and that its division is not North from South as might be expected, but East from West.  An unexpected division of a line that has unintentionally divided more than just Pennsylvania and Maryland

We are a nation of divisions and the Mason Dixon Line is our ur-dividing line.  The one colonial boundary dispute among many – each with its own line – that we remember.  We are northerners and southerners; east coasters and west coasters; red staters and blue staters.  Thomas Jefferson wrote, “a geographical line, coinciding with a marked principle, moral and political, once conceived and held up to the angry passions of men, will never be obliterated; and every new irritation will mark it deeper and deeper.”[x]  Mason and Dixon’s lines are on paper, but they are also drawn indelibly in carbon black ink on the landscape of our minds.

Daniel Kurt Ackermann

[i] Charles Mason and Jeremiah Dixon, The journal of Charles Mason and Jeremiah Dixon. (Philadelphia: American Philosophical Society, 1969), 211.

[ii] James Veech, Mason and Dixon’s Line: A History, (1857), 45.

[iii] Pamela Young, “Conserving the Mason-Dixon Map,” Colonial Williamsburg, Winter 2006.

[iv] He promised not to talk about it; but felt free to include, in the published version, his own thoughts on the subject of slavery and the advisability of colonization in Africa.  John H. B. Latrobe, The History of Mason and Dixon’s Line (1855), 5-7.

[v] Thomas W. Streeter, “New and Notable: Princeton’s Mason and Dixon Map,” Princeton University Library Chronicle (Winter 1955) 97-99; “Princeton’s Mason and Dixon Map,” The Princeton University Chronicle (Winter 1964) 153-155.

[vi] Rita Reif, “Auctions; Declaration for Sale.,” The New York Times, March 26, 1982, sec. Arts,; “MASON-DIXON MAP FETCHES $360,000,” The New York Times, April 2, 1982, sec. Books,

[vii] Lita Solis-Cohen, Maine Antique Digest: The Americana Chronicles : 30 Years of Stories, Sales, Personalities, and Scandals (Running Press, 2004) 397.

[viii] Christies, “Lot 4: Mason, Charles and Jeremiah Dixon, Surveyors, Manuscript Map…,” in The Forbes Collection of American Historical Documents (New York, NY: Christies Auction House, 2002).

[x] Thomas Jefferson, “Thomas Jefferson to John Holmes,” April 22, 1820,