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Mason Dixon Line Americas Great Divide

The Mason-Dixon Line—America’s Great Divide

Acclaimed historian Edward G. Gray, who passed away unexpectedly at the end of 2023, was an award-winning cultural historian and a professor of early American history at Florida State University. The Wall Street Journal called his latest book, Mason-Dixon: Crucible of the Nation, “a magisterial yet highly nuanced account that ventures back and forth across Mason and Dixon’s fabled demarcation line.”

Author - Editorial Staff

Date - 25 January 2024

Time to read - 6 min

In this excerpt from the book, Gray shows how the Maryland-Pennsylvania boundary—even well before Mason and Dixon had accurately mapped it—carried deep significance as a dividing line.

By 1750, Pennsylvania and the Lower Counties were home to more than eight thousand slaves, more than two-thirds of whom lived in the Lower Counties. ([Quaker John] Woolman’s own Jerseys were home to well over five thousand.) In Maryland, the numbers were much higher. In 1750, more than forty thousand slaves lived in the colony, but the vast majority remained in southern tidewater counties, where 40 to 50 percent of the population was enslaved. In the Lower Counties, where slaves constituted a much higher percentage of the population than in Pennsylvania, they still were only 20 percent of the total.

Woolman knew there were slaves in Pennsylvania, not to mention in his home province of West Jersey; he surely knew that compared to tidewater Maryland, there were many fewer slaves in northern and western Maryland. He also surely knew there remained slave owners among the Friends of the Delaware Valley. What is important about Woolman’s account, then, is not its intimations about a boundary between slavery and freedom but the fact that it presumes any clear boundary between Maryland and Pennsylvania at all.

Woolman’s sense of the boundary was not unique. For decades, travelers had remarked on the stark contrast between Maryland and the provinces to the north. Dr. Alexander Hamilton, a Scottish physician who migrated to Annapolis in 1739, traveled to New Castle in the Lower Counties, which he understood to be a town in Pennsylvania—and he was, technically, correct. While enjoying the comforts of Curtis’s, an inn and ordinary, Hamilton met three Pennsylvanians returning to their homes after conducting some business at the Maryland land office in Annapolis. What Hamilton learned was for Woolman an inviolable truth: Maryland was very different. The problem was not slavery but something more general and ambient, something about the social order of the colony. One could not cross from Pennsylvania or its consort colony, the Lower Counties, without an acute sense of descending the scale of civility. As they ambled through their chatty breakfast with Hamilton, one of the Pennsylvanians, offended by the landlady’s mistaking him for a common laborer, replaced his woolen nightcap with a clean linen one and announced that now “I’m upon the borders of Pensylvania and must look like a gentleman; ’tother was good enough for Maryland, and damn my blood if ever I come into that rascally province again.” This Pennsylvanian’s perspective was shared by his fellow travelers. Maryland was, they all agreed, a place of “immorality, drunkenness, rudeness and immoderate swearing.” In Pennsylvania “no such vices were to be found.” Hamilton did not disagree. He knew this characterization of Marylanders’ manners “was pretty true,” although he had little knowledge of Pennsylvanians beyond his encounter with a few of them at New Castle. When the discussion turned to matters economic, Hamilton had to dissent. The Pennsylvanians believed the soil in their province was “far more productive of pasturage and grain.” This Hamilton dismissed; he well knew the boundary between the two colonies corresponded to no natural or topographical divide. Whether Marylanders’ manners differed from those of Pennsylvanians, the doctor could not say. But what was clear was that Maryland elicited disdain from its northern visitors.

A Map Of That Part Of America Where A Degree Of Latitude Was Measured For The Royal Society
Jeremiah Dixon and Charles Mason, A Map of that Part of America Where a Degree of Latitude was Measured for the Royal Society (London: s.n., 1769). Lionel Pincus and Princess Firyal Map Division, The New York Public Library.

Given the starkness of the transition—the sudden onset of dread and foreboding with the crossing from Pennsylvania into Maryland—it is hard not to conclude that Woolman’s reaction reflected this kind of age-old chauvinism. An intuitive eighteenth-century social science allowed Woolman to conclude that whatever was wrong with Maryland was attributable to an especially evil form of unfree labor. This meant that, for him, there was no separating the moral entanglements of slavery from the society that sanctioned those entanglements. Woolman’s perspective afforded no nuance. To cross from Pennsylvania into the deeply corrupted Maryland was to experience, in a weird and metaphysical kind of way, the dark specter of slavery.

The point is that well before Mason and Dixon had accurately mapped the Maryland-Pennsylvania boundary, it carried deep significance as a dividing line—despite almost a century of evidence that in fact the Maryland-Pennsylvania borderlands were far more united than they were divided. As Hamilton seemed to sense, whatever it was that divided Maryland from Pennsylvania would have been difficult to discern until one descended past the mouth of the Susquehanna River to the complex of waterways through which colonial North America’s tobacco crop made its way to market.

Neither the French and Indian War nor the Mason-Dixon Line did much to alter these demographic and economic facts. By the mid-1770s, the distribution of enslaved populations had changed very little, although the total numbers of slaves had risen, more or less proportionately, throughout the mid-Atlantic and upper southern colonies. The borderlands remained the breadbasket of British America, a place of family farms, where sons, daughters, wives, and mothers labored alongside servants and the occasional slave, but the region was not shaped in any obvious way by the institution of slavery. In the terms formulated by historian Ira Berlin, the borderlands were societies with slaves, but they were not slave societies.

Beginning in the mid-1770s, the perception that the crossing of the Mason-Dixon Line involved much more than the transit from one British province to another would receive new and far-reaching credence. The campaign begun by Woolman and his coreligionists would accelerate, as radical proponents of constitutional reform adopted fundamental tenets of Quaker antislavery doctrine. These tenets would become settled law when, in 1780, the Pennsylvania House of Representatives passed the Act for the Gradual Abolition of Slavery, the Western world’s first statutory act of abolition. For the first time, the boundary line created by Charles Mason and Jeremiah Dixon came to resemble in law what the likes of Woolman long claimed it to be: a line between slavery and freedom. But, as with just about every assumption related to the Mason-Dixon Line or any other geopolitical demarcation, even this one demands qualification.

The Gradual Abolition Act’s passage did not abolish slavery in Pennsylvania, nor did it alter the nature of slavery in the borderlands. Insofar as the act transformed Pennsylvania into a “free” state, it did so slowly and haltingly. Decades would pass before a traveler, otherwise uninformed, would have reason to conclude that in crossing the Line she crossed from a free state to a slave state. If anything, the Revolutionary War and subsequent economic change did far more to unify the borderlands than to divide them. Nonetheless, if Pennsylvania’s Act for the Gradual Abolition of Slavery did not quite transform the Line into a boundary between freedom and slavery, it did transform the Line into a boundary between a legal regime largely tolerant of the enslavement of human beings and one that, at least by statute, was the least tolerant of human bondage of all the new American states. For this reason, any understanding of exactly how the Line came to be a line between slavery and freedom must begin with the story of why Pennsylvania enacted such a law and why Maryland and the state of Delaware, as the Lower Counties declared themselves after independence, did not.

Mason Dixon By Edward G  Gray
Edward G. Gray was the author of acclaimed books on the revolutionary era and the early American republic, including The Making of John Ledyard: Empire and Ambition in the Life of an Early American Traveler and Tom Paine’s Iron Bridge: Building a United States. He was Professor of History at Florida State University. Photo by Stacey A. Rutledge.