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Mapping the 1850 Fugitive Slave Act

Digital history projects not only contribute to scholarly debates by approaching familiar questions from new angles, but they also offer one of the best ways to introduce primary sources into the classroom. Think of it this way: your students would probably groan in agony if you assigned them a spreadsheet with row after row of primary source data, but I’d bet their reaction would be quite different if you asked them to browse an interactive map. Some students will zoom out and take in the big picture, while others will hone in on the most minute detail. The upshot is that nearly every student will take away something different, making for great classroom discussion.

While I had long found digital history projects to be useful teaching tools, I eventually made the transition from digital history-admirer to digital history-creator.[1] The opportunity to try my hand at digital mapping first came my way in my capacity as assistant director of the National Park Service (NPS) project Slave Stampedes on the Southern Borderlands. (Abolitionists and slaveholders alike labeled mass escapes “stampedes,” a metaphor which may give some modern readers pause for its connotations of animalistic behavior. However, the term also became shorthand for the growing phenomenon of group escapes, which Northerners and Southerners widely understood as a form of mobile slave insurrection.) Using the data we had amassed from runaway slave advertisements and newspaper reporting, I designed ArcGIS maps visualizing the extent of group escapes from the antebellum South. Our national map shows group escapes from 1847–1865, with icons sized according to the number of participants. Users can zoom in and select individual markers to read a short description of each group escape, and find a link to our database where they can read the original source material. The map highlights the prevalence of group escapes, which often resembled mobile slave rebellions, challenging scholars and students to rethink what we know about the Underground Railroad. Not only did enslaved people frequently escape together in large groups, but they often did so heavily armed and prepared to fight off pursuers.

More than 2,000 abolitionists, including Frederick Douglass (seated), gathered at Cazenovia, New York, in August 1850 to protest the proposed new Fugitive Slave Act. The massive demonstration foreshadowed how Black-led antislavery vigilance committees would oppose—and ultimately undermine—the law’s draconian provisions. Photograph by Ezra Greenleaf Weld, courtesy of House Divided: The Civil War Research Engine at Dickinson College.

The ArcGIS maps I produced for the NPS project made me think that a similar resource might shed light on a question that had long puzzled Civil War scholars: why secessionists across the Deep South cited the purported failures of the 1850 Fugitive Slave Act as one of their primary reasons for leaving the Union. After all, most enslaved people escaped from the border slave states, not the Deep South, and the total number of successful escapes throughout the 1850s hovered between one thousand and three thousand people per year at most. Costly as escapes were to border state slaveholders, those numbers hardly made a dent in the U.S. South’s overall enslaved population, which was fast approaching four million. More puzzling still, the 1850 Fugitive Slave Act seemed to meet all of slaveholders’ demands. The law authorized a massive expansion of federal criminal law enforcement to capture and return fugitive slaves who had escaped into the northern states. Moreover, the law financially incentivized U.S. commissioners to find in favor of slaveholders (federal officials earned ten dollars for every person they remanded to slavery, compared to just five dollars for each person they released). So, why did slaveholders across the Deep South insist that the Fugitive Slave Act was a “dead letter,” and rank the “nullification” of the law as one of their top reasons for leaving the Union?[2]

In an effort to answer that question, I created a new database of fugitive slave cases and mapped that data through ArcGIS. Creating that dataset and mapping it helped me refine the argument which I laid out in my recent JAH article, “Fugitive Slave Renditions and the Proslavery Crisis of Confidence in Federalism, 1850–1860.”

Right from the beginning, I realized that mapping the fugitive crisis would require reassessing what we knew about the total number of people arrested under the 1850 law. For decades, scholars in search of hard numbers about the law’s enforcement had turned to Stanley Campbell’s The Slave Catchers (1968).[3] I could have simply mapped Campbell’s caseload data, but I had already noticed small discrepancies in his numbers. To be sure, Campbell’s painstaking efforts to cull reports of fugitive cases from major newspapers remain an impressive feat. Anyone who has ever sat over a microfilm reader for hours on end, neck craned and eyes squinting, can appreciate just what Campbell accomplished in the pre-digital era. But the mass digitization of newspapers provides us opportunities unavailable to Campbell, including access to countless rural papers which also reported on fugitive cases. As a result, I decided to compile my own caseload data, using as starting points Campbell’s appendix and the running list of fugitive cases kept at the time by abolitionist Samuel May.[4]

In an attempt to impede enforcement of the 1850 Fugitive Slave Act, antislavery vigilance committees routinely charged federal officials with assault and kidnapping in state and local courts. Philadelphia vigilance leaders pressed charges against federal deputy marshals for assault and battery on runaway William Thomas in 1853. The federal officers spent the next nine months in and out of state prison before a federal judge finally dismissed the case against them. Photograph by Cooper Wingert. (Deposition of William Gildersleeve, Oct. 12–13, 1853, United States ex. relat. Jenkins & Cresson, v. Chollet, entry 42-E-11-8.1 and 42-E-11-9.8, box 1, Habeas Corpus Files, 1848–1862, Records of the U.S. Circuit Court for the Eastern District of Pennsylvania, Records of the District Courts of the United States, National Archives, Philadelphia).

I explain how I arrived at a different case count than Campbell in greater detail in my JAH article, but the process of compiling a new dataset opened my eyes in more ways than just revising the overall numbers. While compiling my database, I noticed compelling patterns in the data which did not track with received wisdom about the law’s draconian footprint. As I pored over newspaper reporting and case files, I created columns in my spreadsheet to track emerging themes. Black-led antislavery vigilance committees and sympathetic white allies pressured their neighbors serving as U.S. commissioners to deviate from the law’s harshest provisions. Antislavery attorneys elbowed their way into federal hearing rooms. Black witnesses took the stand on multiple occasions and testified on behalf of alleged fugitives. Rendition hearings that were supposed to be “summary” sprawled out over days, weeks, and even months. All the while, antislavery vigilance committees slapped federal officials and slaveholders with charges for kidnapping and assault in state and local courts. The charges did not always stick, but the threat of legal retaliation clearly slowed the operations of the federal law. Federal officers were increasingly reluctant to take up fugitive cases, and slaveholders even fretted about the potential legal ramifications of pursuing runaways in northern states.

Most arrests under the 1850 Fugitive Slave Act (represented by black dots) occurred in clusters near the border, where U.S. commissioners relied heavily on local constables, firemen, and slave catchers to recapture runaways. Map based on Wingert Caseload Database, created using ArcGIS software and Light Gray Canvas Basemap, Ersi. An interactive version of this map may be accessed here.

Mapping my revised dataset made it even clearer where my findings diverged from the scholarly consensus about the law’s operations. Just a cursory glance at the finished product reveals that most fugitive cases occurred in clusters near the border. If my map gives the impression that the 1850 law functioned more like a series of local slave catching operations than the national slave rendition system that proslavery lawmakers envisioned, that is because it did. Although the law authorized a drastic expansion of federal criminal law enforcement throughout the northern states to recapture and return runaway slaves, no such expansion ever actually occurred. Indeed, the most common outcome when slaveholders headed north to reclaim fugitive slaves under the new law was that slaveholders were never able to find a U.S. commissioner, or one who was willing to take on their case; slaveholders often headed home empty-handed and embittered.

This detail from an engraving published in Boston depicts the May 1854 arrest of runaway Anthony Burns. Federal officials in Boston lacked the manpower to seize Burns on their own, and instead deputized notorious slave catcher Asa Butman and local teamster Caleb Page to make the arrest. Courtesy of Library of Congress.

Even when U.S. commissioners agreed to hear cases, the federal government simply lacked the manpower to pull off arrests on its own and was dependent on assistance from state and local authorities or non-state actors such as slave catchers or firemen. That posed a problem because Northern states like Massachusetts and Pennsylvania had adopted personal liberty laws prohibiting state officials from assisting in fugitive slave renditions, or even using state jails to detain runaway slaves. For example, in August 1851, U.S. Commissioner Richard McAllister could not use Pennsylvania prisons and instead detained fugitive William Smith (alias Bob Sterling) overnight in a Harrisburg hotel. The hotel was far less secure than a prison, so much so that Black activists nearly managed to rescue Smith by setting fire to the building.[5] Meanwhile in Philadelphia, U.S. Commissioner Edward Ingraham was always short on officers to execute his arrest warrants and frequently deputized members of a pro-Democratic Southwark fire company to seize runaways.[6] Given the dearth of federal resources, enforcement of the 1850 law was largely limited to cities like Harrisburg, Philadelphia, Cincinnati, and New York, where U.S. commissioners like McAllister and Ingraham could lean on off-duty local constables, firemen, and seasoned slave catchers to capture fugitives.

This 1851 engraving mocks federal efforts to enforce the Fugitive Slave Act, depicting a gruff-looking federal official with a star on his hat, rope in one hand, and shackles in the other, riding on the back of Massachusetts senator Daniel Webster (who controversially supported the law). Frederick Douglass and William Lloyd Garrison (left) are depicted protecting an enslaved woman from recapture under the law. Courtesy of Library of Congress.

Creating a dataset and then mapping that data helped me sharpen my argument in my recent JAH article. Slaveholders were less troubled by the actual number of escapes. Instead, slaveholders were concerned more broadly about the place of slavery in American federalism. Black and white northerners’ success at undermining the federal law raised fundamental questions about the security of slave property interests in a federal system that allowed for considerable local variation. Enslavers never doubted that the federal government remained their staunch ally in the protection of slave property, but slaveholders increasingly questioned the sufficiency of any federal commitment, no matter how strong, to protect slavery from mounting northern opposition. Slaveholders’ property rights “are wholly disregarded by the people of the Northern States,” declared Georgia secessionists in 1861, “and the Federal Government is impotent to maintain them.”[7] My mapping project helped me see that pronouncements such as this one were not simply melodramatic posturing, but grievances rooted in slaveholders’ actual experiences with the law. Slaveholders weren’t just show-boating, in other words—they were accurately describing the gap between what the law promised and how it actually operated.

In short, mapping projects like mine can add value to scholarship while also making that scholarship more accessible to teachers and students. Compiling data on fugitive slave renditions and mapping it positioned me to address a question to which the field did not yet have a fully satisfying answer. The finished map helps us visualize exactly how and where Black-led resistance undermined the law’s operations. That visual may help students and scholars better grasp why slaveholders found the law’s failures so alarming and why they began reconsidering the future of slavery in a decentralized federal system.

Cooper Wingert is a Ph.D. candidate in the history department at Georgetown University. He is a historian of slavery, federalism, and state-building during the Civil War Era. His in-progress dissertation examines how wartime freedom seekers and Union army provost marshals navigated civil-military tensions and brokered emancipation in the field, and in the process renegotiated and reinvented federalism in the United States. Wingert is the author of several books, including Slavery and the Underground Railroad in South Central Pennsylvania (2016). He currently serves as Assistant Director of the National Park Service project Slave Stampedes on the Southern Borderlands.

[1] The list could go on, but a few key digital history projects that inspired my own efforts include: Mapping Occupation,; The Valley of the Shadow,; Visualizing Emancipation,; and Fugitive Federals,

[2] “The Fugitive Slave Law a ‘Dead Letter’—A Case in Point,” Romney (VA) Intelligencer, reprinted in Richmond (VA) Whig, Sept. 7, 1855, p. 4.

[3] Stanley W. Campbell, The Slave Catchers: Enforcement of the Fugitive Slave Law, 1850–1860 (1968).

[4] Campbell, Slave Catchers; Samuel May, The Fugitive Slave Law and Its Victims (1856–1861).

[5] “Another Slave Case,” Harrisburg (PA) Keystone, Aug. 12, 1851, p. 2.

[6] Minute Book of the Franklin Fire Company, 1838-1854, Sept. 17, 1850, March 14, 1851, March 12, 1852, July 14, 1854, Fire Companies of Philadelphia Collection, Collection Number 0205 (Historical Society of Pennsylvania, Philadelphia). For further insight on Southwark Fire Companies in the antebellum era, see Bruce Laurie, “Fire Companies and Gangs in Southwark: The 1840s,” in Allen F. Davis and Mark H. Haller, eds., The Peoples of Philadelphia: A History of Ethnic Groups and Lower-Class Life, 1790–1940 (1973), 71–87.

[7] Journal of the Public and Secret Proceedings of the Convention of the People of Georgia (1861), 112.