When Maryland Almost Got Philadelphia: The Remarkable Story of the Mason-Dixon Line
It takes a shrewd fellow indeed to persuade the King of England to grant him a charter to all the land in the New World between the colonies of Maryland and New York. When Quaker William Penn II did so, he became the founder of the colony of Pennsylvania in March 1681—thereby securing repayment of his father’s loan to King Charles II of 16,000 pounds sterling (worth about $2.1 million today). But Penn’s acquisition did not go smoothly, for a boundary dispute erupted with the Calverts of Maryland, to the south, that would drag on for 82 years.
Resolution, so long in coming, gave the nation the Mason-Dixon Line, today the unofficial boundary between north and south. References to the Line permeate our culture—witness Thomas Pynchon’s 2004 novel of that name; a character in the 2006 film, “Rocky Balboa”; a shout-out in Johnny Cash’s song, “Hey Porter”; and the duet by Mark Knopfler and James Taylor (the former of the band Dire Straits), “Sailing to Philadelphia,” with lyrics recounting the journey of Charles Mason and Jeremiah Dixon from England to resolve the dispute.
Calvert’s charter was bounded by the Potomac River to the south and the 40th parallel of latitude to the north. Penn’s went from the 42nd parallel south to the 40th, with his southern boundary intersecting a circle having a radius of twelve miles from the center of New Castle. The 40th parallel was to be the boundary between the two colonies—and because it lay five miles north of Philadelphia, Maryland could lay claim to that city.
Here problems arose: Maps of that period were based on maps done in the early seventeenth century by Capt. John Smith; on those the 40th parallel did not intersect a circle having a twelve-mile radius from New Castle (one can easily imagine the difficulty of sorting out boundaries over a wide geographic area with no natural line of division, such as a river). Penn understandably worried about the danger of losing the city and port of Philadelphia, since it lay below that crucial 40th parallel.King Charles instructed Charles Calvert, the third Lord Baltimore, and Penn to work out a mutually acceptable boundary between the colonies. Penn struck quickly: He sent letters to leading citizens of Maryland’s three northeastern, or “lower” counties (now the state of Delaware), informing them that they were, in fact, living in Pennsylvania and thus must cease paying taxes to Maryland. Lord Baltimore countered with instructions not to pay Penn, and that he would be around to collect taxes due him. Further troubles for Lord Baltimore: His title to what is now the state of Delaware was challenged by the Duke of York, the brother of King Charles (and soon to become King James II), who lay claim to the three lower counties.
After conferences between Penn and Calvert in 1682 and 1683 went nowhere, the King’s Board of Trade and plantations issued an edict in 1685 endorsing Calvert’s claim to the boundary nineteen miles to the north, putatively giving Calvert Philadelphia. But Calvert inexplicably failed to conduct a proper survey to authenticate the claim; the eventual border would be established 19 miles further south, with his descendants (who include this writer) deprived of land now irretrievably in Pennsylvania.
Charles Calvert, the fifth Lord Baltimore, petitioned King George II in 1731 for help in demarcating the final boundary. Again a commission was created to study the matter but was unable even to agree on how to properly instruct surveyors. The next twenty years saw more talk peppered by disputes over arcane surveying details such as whether measurements should be made by chaining up and down valleys or by straight horizontal chaining. Resolution remained elusive, for the precise location of the 40th parallel remained an intractable issue. Levels of cross-border violence were rising. The Astronomer Royal was asked to recommend scientific surveyors who could tackle the complex task of surveying and establishing an acceptable boundary between the two colonies, men whose experience and gravitas would definitively settle the issue.
Enter Charles Mason and Jeremiah Dixon. Both had long records of distinguished service at the Royal Observatory at Greenwich. They signed a contract in 1763 and arrived in North America in November of that year. They would spend the next 58 months establishing enduring boundaries of Pennsylvania, Maryland, Delaware and Virginia (now West Virginia), earning enduring fame as the creators of the Mason-Dixon Line, the de facto border between northern and southern America and a disquieting reminder of our nation’s ugly legacy of slavery.
Mason and Dixon began their work at the southernmost point of Philadelphia, at the north wall of a house on Cedar Street (now South Street; the house’s location is under I-95 north). Employing sophisticated principles of astronomy, land surveying, plane and spherical trigonometry, geometry and ground measurements—and accounting for the earth’s curvature—their expedition moved slowly and surely west (earlier surveys had marked the boundary from Fenwick Island west, to a spot equidistant between the Atlantic Ocean and Chesapeake Bay called the Middle Point, then north to Philadelphia).
Iroquois guides led the way, followed by axmen felling trees and brush and the survey party itself. Mason oversaw the astronomers; Dixon the land surveyors. The party camped some nights and spent others either under the stars or the roofs of local farmers, who happily seized the downed trees while keeping eyes on their daughters who flirted with the younger members of the surveying party. Work halted during inclement weather and when Mason and Dixon galloped off to apprise the boundary commissioners of their progress.
Charles Mason’s journal, in the National Archives, names many of the landowners the party encountered, and is replete with cryptic references that characterized their work: “At 49 miles 7 chains crossed the lower Road leading from York to Joppa and Baltimore,” reads an entry on July 24, 1765, as the surveying party passed through Baltimore County. Entries five days later: “at 57 miles 66 chains a Branch of Gunpowder” and “at 58 miles 58 chains Mr. Valentine Vant’s House 50 links North.” (A chain measured a distance of 22 yards, while links marked inches.) Wooden posts pounded into the ground served as mile markers.
Stone markers, arriving by barge from England and hauled overland to replace the wooden stakes, were set every mile. The stones were engraved with “P” on the north side and “M” on the south; “crownstones” were set every five miles. Mason and Dixon completed their work in October 1767, having surveyed 233 miles, 17 chains and 48 links, ending just northwest of Oakland, Maryland. Worry over the bellicose intentions of the Lenape Indians, who were being pushed from their lands by settlers, brought an end to their remarkably enduring task.
Several events in October will mark the 250th anniversary of Mason and Dixon’s passage through Baltimore County in the summer of 1765. The Mason and Dixon Preservation Society, the Preservation Alliance of Maryland and Baltimore County will erect a replica stone at Larry Malone’s Mason-Dixon Farm, which has 75 acres in Pennsylvania and 25 in Maryland (the original stone marker number 49 is in the farm’s wheat field, 200 feet west of Interstate 83, accessible for public viewing). The Maryland Historical Trust will erect a sign that describes the meticulous and complex work these two English surveyors and their men performed that summer.
A joint conference of the Maryland Society of Professional Engineers and the Maryland Society of Surveyors will include a reception at the Maryland Historical Society on October 8—among the objects on display will be the Bird Transit, a sophisticated surveying instrument Mason and Dixon used to determine the direction of the meridian, or true north. The Transit, borrowed from Independence National Historical Park in Philadelphia, likely witnessed the first public reading of the Declaration of Independence, on July 8, 1776, on the steps of Independence Hall, where in 1912 it was discovered under the floorboards. David Thaler, a Baltimore engineer who in the course of extensive research on Jeremiah Dixon’s work in England found a dozen surveys Dixon had conducted (two of which had not been seen for 200 years) and took tea with a Dixon descendant, will moderate a panel on the Transit. English surveyor Edwin Danson, the only person to have divined the details of how Mason and Dixon conducted the survey, will lecture and sign copies of his book, Drawing the Line: How Mason and Dixon Surveyed the Most Famous Border in America. (This event at the Maryland Historical Society is open only to conference registrants.) The Bird Transit will be on display until October 18.
The Maryland Historical Society is a rich source of original documents related to this most famous survey in American history. In its collection are two of three extant maps of the Mason-Dixon Survey, signed and sealed by the twelve boundary commissioners; the original contract signed by William Penn, Frederick Calvert and Messrs. Mason and Dixon; and the surveyors’ actual invoice for services rendered. Approximately 300 of the 1,300 documents in the organization’s Calvert Papers relate to the boundary dispute between the Calverts and William Penn. Mason and Dixon’s original journal can be found in the collection of the Maryland State Archives.
The U.S. Coast and Geodetic Survey, part of the National Oceanic and Atmospheric Administration, has endorsed the quality of Mason and Dixon’s work, which resolved a quarrel that lasted more than four score years and whose resolution long eluded kings and earlier surveyors and scientists. While the resolution of this dispute was no doubt a great relief to all parties, Maryland lost 4,300 square miles, and Virginia 1,100 square miles, to Pennsylvania—the outcome of, in the words of Edwin Danson, the “most ambitious geodetic survey ever conducted.” (Charles W. Mitchell)
Charles W. Mitchell is an independent historian. He is the author of “Maryland Voices of the Civil War” and “Travels Through American History in the Mid-Atlantic.”