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Mexico’s surprising role in sparking the US Civil War

Our southern neighbor was chaotic and weak, but its abolition of slavery gave it a powerful moral authority.

A ceiling mural by José Clemente Orozco in Guadalajara's Palacio de Gobierno depicts the signing of laws that abolished slavery in Mexico in 1837.
A ceiling mural by José Clemente Orozco in Guadalajara's Palacio de Gobierno depicts the signing of laws that abolished slavery in Mexico in 1837.Alan Levine/Wikimedia Commons

No one knew how the two sailors escaped — whether they risked swimming from the Metacomet, anchored in the deep water off the port of Veracruz, Mexico, or whether someone had rowed them to shore under cover of darkness. It was the summer of 1857, and the Metacomet was due back in its home port of New Orleans, where another shipment of cotton awaited transport to Mexican markets. But the steamship could not leave Veracruz without the two missing sailors, and the shipmaster had reason to fear that the men were gone for good. Although it had become routine for Mexican authorities to arrest seamen who broke their contracts, George and James Frisby were no ordinary deserters: They were Black slaves — hired out by their owner in Louisiana.

If George and James Frisby had escaped in New York or Boston, they would have been returned, if captured, under the US Constitution and the Fugitive Slave Act, but Mexico’s laws offered no such guarantees. Not only had Mexico abolished slavery, but its laws freed the slaves of other countries from the moment they set foot on its soil. To have any chance of returning the Frisby brothers, the shipmaster of the Metacomet avoided mentioning that the two men were Black slaves. Assuming that the missing sailors were ordinary deserters, the local police promptly apprehended George. But his brother proved harder to find. As the police searched the streets and alleyways of Veracruz, James hid inside a house. Nothing is known for certain about the house or its owners, though there is reason to believe that while in hiding, James learned about Mexico’s antislavery laws. When the police finally found him, he did something that his brother did not: He claimed his freedom by producing evidence of his enslavement.


Since Mexican law abolished slavery and freed all slaves who set foot on its soil, the Commander of the Port of Veracruz refused to arrest James, even when the US ambassador to Mexico protested that the incident would undermine the “increasing and beneficent commerce” between Mexico and the US South.

Much more was at stake than commercial relations. The freedom that Mexico promised would threaten slavery not just in the nearby states of Texas and Louisiana, but at the very heart of the Union.


Determining how many enslaved people actually reached Mexico from the United States is difficult. My estimate, based on scattered and incomplete Mexican sources, puts the number somewhere between 3,000 and 5,000 people — considerably fewer than the 30,000 to 100,000 runaways who crossed the Mason-Dixon Line. Still their collective story had strategic and political significance out of all proportion to the numbers involved. Their experiences reorient our understanding of the Civil War, showing that one of the most distinctively “American” events in US history was in part ignited by the enslaved people who escaped to the south and the laws by which they claimed their freedom in Mexico.

How the South was squeezed

There was no official Underground Railroad to Mexico, only the occasional ally; no network, only a set of discrete, unconnected nodes. Some fugitive slaves received help while making their escape — from free Blacks, ship captains, Mexicans, Germans, gamblers, preachers, mail riders, and other “lurking scoundrels.” Most, though, escaped from the United States by their own ingenuity. They forged slave passes to give the impression that they were traveling with the permission of their masters. They disguised themselves as white men, fashioning wigs from horsehair and pitch. They stole horses, firearms, skiffs, dirk knives, fur hats, and, in one instance, 12 gold watches and a diamond breastpin. And then, while gathering oysters or collecting firewood or walking to a camp meeting, they disappeared.


Two options awaited most runaways in Mexico. The first was to join the military colonies, a series of outposts that the Mexican government established to defend its northeastern frontier against foreign invaders and “barbarous” Indians. The second was to fill Mexico’s labor shortage by seeking employment as servants and day laborers. Both alternatives came at a cost. The demands of military service along the northeastern frontier constrained the autonomy of former slaves. Runaways who worked as servants endured other forms of coercion. In parts of southern Mexico, such as Yucatán and Chiapas, indentured servitude sometimes amounted to slavery in all but name.

Black slavery had previously existed in Mexico. It took root in the viceroyalty of New Spain (as Mexico was then known) at the end of the 16th century, when a series of epidemics decimated the indigenous population that had provided the bulk of the viceroyalty’s labor force. Between 1580 and 1640, New Spain imported more slaves than any other European colony in the Western Hemisphere except Brazil. But after 1640, a decline in sugar prices and an increase in the indigenous population slowly shifted New Spain’s labor system away from Black slavery. As former slaves became free laborers, they formed Black militias; they joined lay religious organizations known as cofradías; they worked as butchers and barbers, domestic servants and ranch hands; and they married people of European and indigenous descent.


By the time Mexicans took up arms against Spain in 1810, Mexico’s population of eight million included only around 9,000 to 10,000 Black slaves. Though the enslaved population was comparatively small, Mexican leaders could not abolish slavery outright. Like the United States, Mexico was founded on two competing principles — liberty and property. In both countries, masters insisted that enslaved people be counted as chattel — that is, movable property.

Slaveholders in the United States capitalized on this logic to argue that any interference with slavery amounted to a violation of property rights. In 1787, when the Continental Congress prohibited slavery north of the Ohio River, disgruntled slaveholders convinced the territorial governor that the measure did not apply to enslaved people already in the region. Eleven years later, the US Congress rejected a bill to abolish slavery in the Mississippi Territory, after slaveholders around Natchez made clear that they would sooner revolt than submit to such a measure. In 1804, Congress succeeded in prohibiting the importation of slaves to the Louisiana Territory, but reversed course the following year in the face of resistance from slaveholders. Pressured not to interfere with the “peculiar institution,” Congress hesitated to abolish slavery or even to enact gradual emancipation policies.


In Mexico, slaveholders also opposed any interference with their “property,” but local and national authorities did not comply with these demands as often as politicians in the United States did. The threat of a revolt convinced Mexico’s leaders that the only way to ensure political stability was to bring slavery to a gradual end. Between 1824 and 1827, more than half of Mexico’s states promised that the children born to enslaved people would be free — a law that would end slavery within a generation. Meanwhile, Mexico’s Congress prohibited the introduction of enslaved people to the republic, promising freedom to illegally imported slaves from the moment they set foot on the national territory.

As Mexican politicians tried to enforce gradual emancipation policies, Anglo-American slaveholders who had moved to the Mexican province of Téjas in the 1820s and 1830s realized that the future of slavery was not as assured in their adopted country as it was in the United States. In the fall of 1835, the Anglo colonists revolted, and a year later, declared their independence. The Texas Revolution confirmed the danger that slaveholders posed to Mexico.

In 1837, Mexico’s Congress prohibited slavery across the nation. This abolition policy boosted morale among Mexicans, galvanized international support for Mexico, and encouraged slaves in Texas to revolt or escape. But Mexico’s attempts to undermine slavery in Texas gave credence to rumors that another foreign power — Great Britain — was scheming to promote abolition in Texas, in violation of the Monroe Doctrine. To prevent such interference, the US Congress voted in favor of annexing Texas in 1845. Within a year, war broke out between Mexico and the United States.

Southern planters predicted that the war with Mexico would extend slavery to the Pacific. Instead, the conquest of Mexican territories threatened the very existence of slavery in the United States. US congressmen from Northern states refused to reestablish slavery where it had been abolished, including in the territories that the United States seized from Mexico. And when Southern politicians attempted to extend slavery into the former Mexican territories they ignited a sectional controversy that would lead to the overturning of the Missouri Compromise, the outbreak of violence in Kansas, and the birth of a new political coalition, the Republican Party, whose success in the election of 1860 led to the US Civil War.

The histories of Mexico and the United States continue to seem distinctly unrelated. Mexico was so unstable that 49 presidents took office between 1824 and 1857, while the United States enjoyed political stability and economic prosperity. In the first half of the 19th century, the population of the United States doubled and then doubled again; its territory expanded by the same proportion, as its leaders purchased, conquered, and expropriated lands to the west and south. By almost every metric, the United States was stronger than Mexico, and according to most accounts, the US government could impose its will on its Latin American neighbors without consequence.

But Mexico’s relative lack of power did not mean that it was powerless. Power can take on other, subtler forms than economic success or brute force. In the 19th century, newly independent Mexico gained moral power through the rejection of slavery. These policies would alter the lives of enslaved people in Texas and Louisiana, and ultimately obstruct the expansion of slavery across the southwestern United States.

We cannot understand the coming of the Civil War without taking into account Mexico and the slaves who reached its soil. America’s histories of slavery and sectional controversy are, in fact, Mexican histories, too.

Alice L. Baumgartner is assistant professor of history at the University of Southern California. This essay is adapted with permission from her book “South to Freedom: Runaway Slaves to Mexico and the Road to the Civil War,” published by Basic Books. Copyright © 2020 Alice L. Baumgartner.