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 Ancient Society of Pennsylvania steered into the storm. That November thay 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 instantly. 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
The Accidental Colony: How Geography and Ambition Shaped Pennsylvania
William 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 thes 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
## The Shifting Border: Slavery and Freedom Along the Mason-Dixon Line
The Mason-Dixon Line, today synonymous with the division between North and South, emerged from a complex history of surveying, political negotiation, and evolving social dynamics.Its story isn’t simply about a newly drawn border, but of the line’s metamorphosis during the nineteenth century. The number of enslaved people in pennsylvania and Maryland surged in the 1750s and 1760s, with Maryland’s tobacco producers ensuring slavery continued to dominate the labor systems of the Tidewater and the Eastern Shore. By the American Revolution, Pennsylvania held around seven thousand enslaved people, while Maryland’s population exceeded seventy thousand.
However, in the borderlands, population growth was driven by white immigrants and, increasingly, by industrialization. Travelers entering Lancaster, Pennsylvania, in the 1780s were surprised to find thriving communities of watchmakers, coopers, gunsmiths, rope makers, and printers. While enslaved people lived on both sides of the line, wage laborers primarily worked the fields, mills, forges, and factories that made this region the most economically vibrant in the new United States.Following the Revolution, Pennsylvania passed a gradual emancipation law, and Maryland eased restrictions on enslavers manumitting their slaves. Slavery’s grip seemed to be loosening on both sides, with the primary competition becoming which state could best capitalize on the borderlands’ commercial potential.
before the Revolution, this wasn’t a contest; Philadelphia was the preeminent commercial city on the North American mainland. But the war brought important disruptions to Pennsylvania, including the British occupation of Philadelphia from 1777-1778.Baltimore, by contrast, remained unseized and unblockaded, and the borderlands’ river systems facilitated trade, allowing farmers to access Maryland’s commercial capital more easily. When the US Constitution’s comity clause affirmed the right to trade freely across state lines,Pennsylvania’s interior wealth flowed southward-so much so that Gray describes the border region as “Greater Baltimore.” Philadelphia would eventually need canals and railroads to regain 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 existed from the borderlands to Baltimore, but it struggled to gain traction in the state’s southern tobacco counties and the Eastern Shore. Consequently, a boundary between slavery and free labor-and, more broadly, between proslavery and antislavery ideologies-ran through Maryland, rather than between Maryland and Pennsylvania. As Pennsylvania’s 1780 abolition law slowly took effect, the Mason-Dixon Line became a beacon for enslaved people across the upper South, gradually assuming an antislavery importance.
In Maryland, enslaved people’s resistance varied depending on their circumstances. Some persuaded their enslavers to manumit them or limit their service in exchange for a promise not to escape north. Others negotiated with unyielding owners, living in constant fear of being sold into the Deep South’s cotton complex. two of the most celebrated fugitives, Harriet Tubman and Frederick Douglass, risked everything by fleeing Maryland’s Eastern Shore and crossing the Mason-Dixon Line. Simultaneously, manumissions led to a substantial increase in Maryland’s free Black population, alongside a white-led movement to expatriate African Americans-both freeborn and manumitted-to Liberia.As legislators grappled with the logistics of this colonization scheme-by 1840, over 150,000 free and enslaved people resided in the state-the dynamics of slavery on the ground became increasingly volatile. More and more enslaved people attempted daring escapes to freedom, while enslavers intensified their surveillance, threats, and punishments against anyone challenging their authority.
By the 1830s, the steady stream of fugitives heading from maryland to Pennsylvania meant that, as Douglass later recalled, “h
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