American History Is Black History: The Mason Dixon Line
S. E. Anderson
The Most Rancorous Line
Nicholas Guyatt
January 15, 2026 issue of The New York Review of Books
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Mason-Dixon: Crucible of the Nation
By the fall of 1854, most Americans realized that their nation’s protracted effort to avoid open conflict over slavery was failing. The passage of the Fugitive Slave Act in 1850 and the publication of Uncle Tom’s Cabin two years later had riled northerners and southerners in turn, and the armed struggle between proslavery and antislavery settlers in the Kansas Territory was just beginning. While many of the nation’s political and cultural elites were still keen to avoid the topic of disunion, the directors of the Historical Society of Pennsylvania steered into the storm. That November they invited John Latrobe, a prominent lawyer from Baltimore, to deliver their annual public lecture. His subject was “The History of Mason and Dixon’s Line.”
Stretching west for nearly 250 miles from the Chesapeake through the Appalachians, the line had been drawn between 1763 and 1767 with unprecedented precision by two English surveyors, Charles Mason and Jeremiah Dixon. Originally intended to settle a boundary dispute between Pennsylvania and Maryland, by 1854 it had assumed an ominous new meaning as the border between the slave South and the free North. “There is, perhaps, no line, real or imaginary, on the surface of the earth…whose name has been oftener in men’s mouths during the last fifty years,” Latrobe declared. (He included the equator.) He urged historians to look beyond the line’s present-day “notoriety” and restore its true purpose: not to divide the South from the North but to plot the course of American settlement into the continent’s vast interior. If Americans could only remind themselves of its original meaning, they would unite again in the enjoyment of the exceptional opportunities offered to them by geography and providence.
Latrobe’s attempt to use the history of the Mason–Dixon Line as a political emollient was wildly unsuccessful. If anything, in subsequent decades the line’s power to signify elemental distinctions—between North and South, freedom and slavery, equality and racial prejudice—only grew. Edward G. Gray’s excellent recent history of the line, which invokes this speech in its introduction, acknowledges the line’s entanglement with slavery to a degree that would have appalled Latrobe. But Gray also wants to convince us that the clash between North and South “represented only part of the Line’s story.” The irony of this border—as with so many others—is that political distinctions had only limited power to shape reality.
The colonies of Maryland and Pennsylvania both emerged from the fast-moving religious currents of seventeenth-century England. George Calvert, the first Lord Baltimore, rose from modest origins to become a courtier and close adviser of James I. He was also a Catholic, and in the early 1620s he decided to found an American colony that might combine profit with a promise of refuge to his coreligionists. His first attempt, in Newfoundland, failed miserably. After a sojourn in Virginia, he returned to England and petitioned the new king, Charles I, for a settlement on the Chesapeake instead. Calvert died in 1632, two months before the king granted his request. Cecil Calvert, the second Lord Baltimore, brought his father’s charter to America. By 1640 the new colony of Maryland—named for Charles I’s (Catholic) wife, Henrietta Maria—had attracted five hundred settlers.
The founding of Maryland created border trouble more or less immediately. The colony’s charter implemented a feudal device from England called the palatinate, by which the sovereign gave a proprietor virtually unlimited power to govern a peripheral region. This was a more sweeping grant than the one given to the Virginia Company in 1606, and Virginian officials were alarmed at what their new Catholic neighbor might do. Could Lord Baltimore even forge an alliance with Spain? Back in London, the Privy Council offered some reassurance by carefully marking the bounds of Baltimore’s domain—the first time the Crown felt the need for clear borders between its American colonies. The Potomac River would divide Maryland from Virginia. What later became known as the Delmarva Peninsula (much of which would eventually become the state of Delaware) was reserved for Maryland—except for the peninsula’s southernmost tip, already settled by Virginians.
According to the charter, Maryland’s northern boundary would be the fortieth parallel, “where New England is terminated.” New England grew tremendously to the west during the seventeenth century, but to the south it never got anywhere near the fortieth parallel, which passes through Philadelphia. Instead it was the Swedish and the Dutch who established the first colonies in the mid-Atlantic region (including the Delmarva Peninsula). In 1655 the colony of New Netherlands overran and absorbed the Swedish settlements in what is now New Jersey. Within a decade, New Netherlands was itself captured by a British naval force in the name of the Duke of York, Charles II’s brother (and the future James II). In the process Delmarva became a disputed territory—not only between European settlers (Dutch and British) and indigenous people but between competing British claimants. The second Lord Baltimore was unwilling to surrender his domain even to the king’s brother, but the Duke of York’s local representative, the governor of New York, insisted that the duke’s conquest of Dutch territory preempted the claims of the Maryland charter. Invoking the same logic of land use with which white settlers denied Native sovereignty, the duke’s supporters argued that the disputed region could not belong to Maryland if Baltimore’s colonists had never settled there. The quarrel took more than half a century and a typically byzantine Chancery suit to resolve.
The skirmishes over Delmarva demonstrate that seventeenth-century European nations were often so preoccupied with religious and political controversies at home that they lacked the focus or capacity to micromanage North American expansion. Colonization therefore became the work of powerful individuals and their representatives and descendants. As Gray points out, this was hardly the “salutary neglect” spoken of by Edmund Burke, the Irish-born member of Parliament who in 1775 warned British ministers against repressing the restive American colonists. It was an uncoordinated, even sclerotic form of governance that frequently left powerful proprietors and land-hungry colonists to settle their own arguments.
Lord Baltimore’s unpleasant dispute with the Duke of York was merely a prelude to the wrangling over Maryland’s northern boundary that followed the creation of Pennsylvania in 1681. Like George Calvert, William Penn was drawn to North America by a combination of wealth and religious unorthodoxy. Penn’s Protestant nonconformism was, if anything, even less desirable in Restoration England than Calvert’s Catholicism had been forty years earlier: Penn’s religious beliefs had gotten him kicked out of Oxford (a place of “hellish darknes & debauchery,” he later wrote) and thrown into the Tower of London. But he could fall back on his famous name. His grandfather had been an influential merchant, and his father was an admiral in the Royal Navy. During the English Civil War Penn’s father had taken up the cause of Parliament, but after the Restoration he atoned for his disloyalty by serving the Crown in a number of positions. His son, meanwhile, shed a little of his youthful zeal, took up the law, and managed his family’s considerable estates. Toward the end of the 1660s William Penn converted to Quakerism, a sect that was popular among English merchants but subject to scrutiny and suspicion from the state.
Penn lobbied for religious toleration in England while scouting opportunities for a Quaker colony overseas. In 1680 he petitioned Charles II for a large grant on the western side of the Delaware River. While Penn later claimed that the king had honored his request in order to discharge an old debt owed to his father, Charles was happy to put an ocean between himself and a group of particularly influential nonconformists. By 1681 Penn had his charter and a blueprint for a colony of unprecedented scale and ambition.
That colony’s most famous settlement—Philadelphia—became the seat of Penn’s American domain only thanks to the era’s rudimentary command of geography. Maryland’s charter had specified that its northern boundary lay at the fortieth parallel, but maps of the region were vague on where exactly this was. Believing the Dutch settlement of New Castle (now under the control of the Duke of York) to be close to the fortieth parallel, and eager to ensure that its residents would have some breathing room from the new Quaker colony, the imperial officials who drew up Penn’s charter plotted a twelve-mile radius from New Castle to the Delaware River and created the Delaware Curve, still the only circular border in the continental United States. But New Castle was actually thirty miles south of the fortieth parallel, and so Pennsylvania’s charter had inadvertently seized a major chunk of northern Maryland. Had the fortieth parallel been marked accurately, Philadelphia would have belonged to Lord Baltimore. Instead Penn commissioned a map in London in 1681 that placed the parallel even farther to the south—around fifty miles from its actual latitude. Mason and Dixon would eventually follow the charter’s direction to plot the line from the Delaware Curve, though in the process they confirmed a sizable part of Penn’s sly land grab.
In 1682 Penn disembarked in America and began the work of establishing Pennsylvania. As Gray reminds us, the scale of violence against indigenous people during Pennsylvania’s first decades was limited in comparison with the genocidal colonization of New England and Virginia. In his negotiations with the Lenape Indians who occupied the Delaware River’s western reaches, Penn styled himself as a different kind of European: he wanted the “Love and Consent” of Native Americans as he built out his “great Province.” The colony’s expansion compelled Penn’s successors to test indigenous patience with ever greater demands for land. At first, though, the principal instrument of Pennsylvania’s expansion was the treaty. Penn’s understanding of sovereignty was vastly more exclusive than the one that prevailed among his Native neighbors, and he knew that he was not always negotiating with the Indians who had a rightful claim to the regions he hoped to buy. In these respects, he anticipated the fraudulent treaty making that would define relations with indigenous people for two centuries or more.
Penn’s most urgent territorial challenge after 1682 was to secure his colony’s access to the Atlantic. Philadelphia was more than fifty miles from the ocean, and hostile settlers along the Delaware River might easily threaten Pennsylvania’s commercial viability. Maryland still claimed New Castle and the Dutch settlements on the Delmarva Peninsula; taken together, these became known as the Lower Counties. The Duke of York insisted on his own claim, and Penn had the clever idea of drawing up a lease agreement with the distant duke rather than negotiating with his Maryland counterpart.
Cecil Calvert, the second Lord Baltimore, had died in 1675. His son Charles, the third Lord Baltimore, met twice with Penn in 1682 and 1683 to resolve the dispute, without success. Both men then rushed to London to continue their quarrel before the Lords of Trade, who delivered a broad victory to Penn. The Duke of York was confirmed as the ruler of what would be known as Delaware, and Penn was allowed his leasing arrangement for the Lower Counties, which became political satellites of Pennsylvania. The precise boundary between the new Quaker colony and Maryland remained unclear. For the better part of a century, the fuzziness of that border led to confusion, rancor, and violence on both sides.
Pennsylvania and Maryland each had a commodity with which to anchor colonial trade—furs and tobacco, respectively. The two colonies’ borderlands also offered opportunities to small farmers growing wheat, barley, and flax. In the first part of the eighteenth century, the agricultural boom in southeastern Pennsylvania made these borderlands the fastest-growing part of Penn’s domain: thousands of immigrants from Europe—led by Scots-Irish Protestants—had settled there by 1730. Both colonies attempted to fix these new arrivals within their domains by incorporating counties and collecting taxes, but the uncertainty of the border confounded a precise accounting of who owed what to whom.
Pennsylvania’s governors engaged the region’s Conestoga and Shawnee Indians in trade, legal chicanery, and diplomacy, while broadly respecting the sovereignty of indigenous people who lived in the western reaches of the borderlands. But wildcat settlers from Maryland streamed across the border to take advantage of the rich soils, displacing and killing Indians who had received Penn’s assurances of sovereignty and safety. Without a clear line to demarcate Maryland from Pennsylvania, the economic opportunities of the borderlands threatened to destabilize both colonies and destroy whatever “Love and Consent” remained on the part of Native Americans.
Meanwhile realignments of power among indigenous people left Lenape and Shawnee Indians in an especially vulnerable position. The powerful northeastern Haudenosaunee alliance had forced these nations westward, and Penn and his officials had negotiated treaties guaranteeing their resettlement beside the Susquehanna River in the borderlands. This, however, was precisely where white settlers from Pennsylvania and Maryland staked their claims to the region’s agricultural bounties. Native Americans also grew frustrated with the rogue practices of Pennsylvania’s officials, who became ever more cunning in the practice of treaty making. When Lenape Indians agreed in 1737 to cede an area of eastern Pennsylvania equivalent to the distance a man could walk in a day and a half, John Penn and Thomas Penn—William Penn’s sons and successors—arranged for three seasoned runners to do the “walking,” roughly doubling the cession the Lenape had thought they were making. The same officials were conspicuously slow to address the growing violence against Indians in the borderlands.
This violence reached a crescendo during the French and Indian War, which began in 1754 and bled into the Seven Years’ War (1756–1763). The conflict was driven by competition between Britain and France for control of the Ohio Valley. It began when the royal governor of Virginia sent a military expedition headed by George Washington to the important French outpost of Fort Duquesne, in what is now western Pennsylvania. The French defenders easily held off Washington’s forces—a defeat that tarnished the young Virginian’s reputation and failed to ignite a wave of sympathy across the colonies. (Pennsylvanians were especially reluctant to risk their lives in a war that might aggrandize Virginia.) When British officials finally maneuvered the colonists into a full-blown conflict with France, American settlers and soldiers never lost sight of their local interests. Serving alongside British redcoats, American militiamen waged brutal warfare against the indigenous allies of the French, and colonists took the opportunity to settle scores with even those Native Americans who were living peacefully within the bounds of Pennsylvania.
The outcome was the ethnic cleansing of most of the borderlands Indians. In Philadelphia Benjamin Franklin was appalled by the “murder” of “Numbers of innocent People in cold Blood” at the hands of white vigilantes. Franklin had long opposed the Penn family’s proprietorial rule over the colony, and he invoked the regime’s shameful abandonment of indigenous people to propose that a royal governor now be placed at the head of Pennsylvania’s politics. Given that Philadelphia became the headquarters of a separatist government for a new American nation barely a dozen years later, it’s ironic that in 1764 prominent colonists looked to Britain to solve two of their major problems: Franklin went to England to agitate for a royal governor, a fact that explains Pennsylvania’s surprisingly muted participation in the widespread protests against the Stamp Act the following year; and Pennsylvania’s governor, Thomas Penn, approved the appointment of two British surveyors to finally fix the boundary line with Maryland.
The exploits of those surveyors hold less interest for Gray than a reader might have hoped. In fairness, the notes left by Charles Mason and Jeremiah Dixon from their surveying expedition of 1763–1767 are notoriously flat. “Their journal is the most naked of records,” complained John Latrobe, who resorted to graphology to capture the essence of his heroes. (Mason’s hand confirmed him as “a cool, deliberate, painstaking man…a man of quiet courage,” while Dixon’s signaled “a man of an impatient spirit and a nervous temperament.”) For contemporary readers, Thomas Pynchon’s 1997 novel Mason & Dixon may have raised expectations to unrealistic levels. Did Mason and Dixon really smoke weed with George Washington? (No.) Did Dixon assault an enslaver in Baltimore to facilitate the escape of his slaves? (No.) Pynchon drew license both from fiction and from his highly unreliable narrator, the Reverend Cherrycoke. Gray is the opposite of that “untrustworthy Remembrancer,” though in reading his dutiful account of Mason and Dixon’s journey it’s hard not to miss Cherrycoke’s flair for the dramatic.
This is a minor complaint. Gray’s final chapters offer a thrilling account of the struggles over the newly drawn border and of the line’s metamorphosis during the nineteenth century. The number of enslaved people in Pennsylvania and Maryland had surged in the 1750s and 1760s, and Maryland’s tobacco producers ensured that slavery continued to dominate the labor systems of the Tidewater and the Eastern Shore. There were around seven thousand enslaved people in Pennsylvania by the American Revolution, and more than ten times that number in Maryland.
In the borderlands, however, population growth was driven by white immigrants and, increasingly, by industrialization. Gray recounts the surprise of travelers entering Lancaster, Pennsylvania, in the 1780s and finding watchmakers, coopers, gunsmiths, rope makers, and printers. Enslaved people lived on both sides of the line, but it was principally wage laborers who worked the fields, mills, forges, and factories that made this perhaps the most economically vibrant region in the new United States. In the aftermath of the American Revolution, Pennsylvania passed a gradual emancipation law, and Maryland made it easier for enslavers to manumit their slaves. Slavery’s hold seemed to be slipping on both sides of the line, and the chief contention between Pennsylvania and Maryland was over which could best harness the commercial potential of the borderlands region.
Before the Revolution this was hardly a contest: Philadelphia was the preeminent commercial city on the North American mainland. But the war led to huge disruptions in Pennsylvania, including the British occupation of Philadelphia in 1777–1778. Baltimore, by contrast, was neither seized nor blockaded, and the river systems of the borderlands made it easier for farmers to buy goods and sell their produce through Maryland’s commercial capital. When the comity clause of the new US Constitution confirmed the right of Americans to trade freely across state lines, the wealth of Pennsylvania’s interior drained inexorably southward—to such an extent that Gray describes the border region as “Greater Baltimore.” Philadelphia would eventually require canals and railroads to claw back its share of the interior’s wealth.
By the early nineteenth century Maryland had become, in Gray’s words, “a slave state…in which slavery occupied an increasingly marginal part of the labor economy.” Antislavery sentiment could be found from the borderlands to Baltimore, but it was harder to sustain through the state’s tobacco-growing southern counties and the Eastern Shore. In effect, a boundary between slavery and free labor—and more loosely between proslavery interest and antislavery commitment—ran through Maryland, rather than between Maryland and Pennsylvania. But as Pennsylvania’s 1780 abolition law slowly took effect, the Mason–Dixon Line became a beacon to enslaved people across the upper South and began to assume an antislavery charge.
In Maryland enslaved people’s resistance was closely conditioned by circumstance. Some persuaded their enslavers to manumit them or to limit the length of their service in return for a promise not to escape through the borderlands to the North. Others struggled to negotiate with obdurate owners and lived in constant fear of being sold into the cotton complex of the Deep South. Two of the most celebrated fugitives from slavery—Harriet Tubman and Frederick Douglass—took their chances by fleeing Maryland’s Eastern Shore and crossing the Mason–Dixon Line. But manumissions also produced a huge increase in Maryland’s free Black population, alongside a white-led drive to expatriate the state’s African Americans (whether freeborn or manumitted) to a new West African colony alongside Liberia. (Latrobe became Maryland’s most prominent colonizationist.) As legislators struggled with the logistics of this scheme—by 1840 more than 150,000 free Black and enslaved people resided in the state—the dynamics of slavery on the ground became increasingly volatile. More and more enslaved people made daring flights to freedom, while enslavers intensified their efforts to surveil, threaten, and punish anyone who challenged their authority.
By the 1830s the stream of fugitives heading from Maryland to Pennsylvania meant that, as Douglass later recalled, “hired kidnappers infested the borders.” Gray retells the story of a Maryland enslaver named Edward Gorsuch. In 1849, after Gorsuch became convinced that five bushels of wheat had been stolen from his plantation, four of his enslaved people—a third of his workforce—fled to Pennsylvania. We can’t be sure if they were involved in the theft, but these four men were so scared of Gorsuch’s wrath—and the likelihood that he would sell them into the cotton fields of the Deep South—that they risked everything to escape his reach. With the help of local abolitionists (white and free Black) they settled across the border near the Lancaster County town of Christiana. It took Gorsuch nearly two years to track them down, but in September 1851 he descended upon Christiana and besieged the cabin in which the men had taken refuge. In the ensuing firefight, Gorsuch was killed. At the behest of enraged white southerners, federal officials swept the region and made dozens of arrests. But they failed to find the runaways (who escaped to Canada), or to convict anyone for Gorsuch’s murder.
The Christiana “riot,” as it was termed by disapproving newspapers in the North and South alike, vividly illustrated the line’s new significance. Gorsuch had marched into Pennsylvania invoking the 1850 Fugitive Slave Act, which put federal officials and resources at his disposal even in a free state. Only a fraction of white Pennsylvanians counted themselves abolitionists in the early 1850s, but the Fugitive Slave Act and other federal concessions to the South had diminished the middle ground on which an apathetic white bystander might have formerly stood. When Latrobe addressed the Historical Society of Pennsylvania in 1854, the Marylander’s views were broadly similar to those of his Philadelphia audience: slavery was a terrible problem, and the gradual emancipation (and removal) of Black people was the best solution. But the line reduced complex equations and equivocations into an elemental division between slavery and freedom, confounding Latrobe’s hope that Mason and Dixon’s true achievement—the plotting of American settlement into the west—might still hold the nation together.
Gray’s final chapters remind us just how important the line became to the collapse of the Union and the war that followed. From Christiana to Harpers Ferry to Gettysburg, the Pennsylvania–Maryland border became one of the conflict’s central battlegrounds. On his way to assume the presidency in February 1861, Abraham Lincoln had to be smuggled through Maryland. His suspension of habeas corpus in his first months in office was partly directed at the state’s influential secessionist minority, and the precarity both of his presidency and of his continuing presence in Washington—bordered on all sides by slave states—nourished his caution.
By the time Lincoln made serious moves toward emancipation in the fall of 1862, most Marylanders recognized that joining the Confederacy would be a disaster for their state. The brutality of the war and the creeping success of the Union armies marginalized Maryland’s proslavery radicals, and by October 1864 Lincoln had the satisfaction of seeing the state approve a new constitution that enshrined immediate emancipation. Delaware truculently declined to ratify the Thirteenth Amendment until 1901, but when the Civil War came slavery retained only a tiny footprint in that state. After West Virginia achieved statehood in 1863 slavery had no presence whatever across the rest of the line, which for its entire length ran through states that remained in the Union. The hopes of Confederates that the Mason–Dixon Line might become an international border were resoundingly defeated.
Latrobe wrapped up his 1854 speech by ventriloquizing Mason and Dixon. “Our line of survey,” he had his subjects tell the audience, should inspire “a people blessed beyond all others” to occupy “the proudest place among the nations.” But even beyond the bloody decade that followed, the Mason–Dixon Line continued to cast shadows on this bright vision. Maryland, like other states of the upper South, enthusiastically embraced Jim Crow: it established a separate school system for Black children after 1872, even as Pennsylvania passed its landmark law abolishing school segregation in 1881. The descent of the South into racial revanchism for the better part of a century after the Civil War gave the line a renewed power to divide the nation, which in turn made it easier for northerners to overlook the persistence of racial discrimination in their own states. Edward G. Gray, who died in December 2023, leaves this more recent story for other historians. But his book—with its abiding recognition of continuities as well as differences across the border—offers profound insights into how it might be told. ///
s. e. anderson
author of The Black Holocaust for Beginners
www.blackeducator.org
"If WORK was good for you, the rich would leave none for the poor." (Haiti)
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