Guerrero could be best known for any number of things.

Located on Mexico’s southwest coast, the state is the most topographically uneven region in Mexico. More of Guerrero is mountainous than not. The Sierra Madre del Sur mountain range subsumes the state’s territory, leaving only 20% of the land flat enough for commercial agriculture. This vast montane ecosystem is a biodiversity hotspot, featuring cloud forests at the highest peaks, pine-oak forests between 1,900 and 2,500 meters, and tropical deciduous forests at lower elevations.

Guerrero is also unique for having the highest concentrations of Afro-descendants (afrodescendientes) in Mexico. During the 16th century the population of about 200,000 enslaved Africans in New Spain far exceeded Spaniards and was, for some time, the largest black population in the Americas. People of African descent played critical roles in Guerrero and the rest of New Spain as plantation laborers, mine workers, coastal militiamen, and arrieros. As a common pathway for formerly enslaved afrodescendientes, arrieros were also connected to emancipation and social mobility. The movement of afrodescendiente arrieros connected all three workscapes—plantations, mines, and the coasts (via ports)—to Indigenous hamlets and self-emancipated afrodescendiente communities embedded in the forests and hills.

Guerrero is also one of two Mexican states named after arrieros of African descent who fought against the Spanish empire: Vicente Guerrero and José María Morelos. Before he spoke military, Vicente Guerrero spoke the languages of landscape, liberation, and local Indigenous populations. Guerrero used his skills as an arriero to wage guerrilla warfare against the Spanish and eventually became the first Afro-Indigenous president in the Americas. Like other arrieros who fought the Spanish empire in what is now Peru and Colombia in the 1810s, both Guerrero and Morelos relied on their intimate knowledge of environments and communities in southern Mexico to rally troops and evade Spanish forces. According to historian Peter Guardino, arrieros’ support for insurrection seems to have been rooted in their resentment toward the commercial domination of Spanish merchants in Mexico City and Acapulco. No matter their motivation, independence would not have taken place when it did and how it did without the arrieros, especially those who mobilized afrodescendiente sharecroppers.

Insurgents were not alone in taking refuge in Guerrero’s craggy peaks and valleys. It has long been known that the Sierra Madre del Sur offers sanctuary to migratory monarch butterflies, but scientists are increasingly realizing the mountains also protect nearly 43% of all amphibian species in Mexico, 34% of all reptile species, and hundreds of other endemic species.

Unfortunately, more people know Guerrero for its tourism, violence, and other extractive industries. For many, Acapulco lives in the imagination as a site of picturesque palm trees, white beaches, and blue waters. For many others, however, Acapulco is the biggest city in a state known for drug cultivation, organized crime, viciously rival gangs, and thousands of disappeared people.

Even before Acapulco gained this reputation, Mexican officials had presumed Guerrero to be a bad place where bad, and often black, things happen. Sociologist Armando Bartra coined the term “Guerrero bronco” to describe how politicians and military officials have imagined the state as an ungovernable region since the independence period. A bronco or cimarrón is an untamed horse, which in Spanish is meant to allude to Guerrero as an unbroken, unpolished, and rough state where violence takes the place of state presence and economic development. It’s no coincidence cimarrones was also a name given to self-emancipated runaways. However, Bartra’s work articulates quite the contrary. Violence in Guerrero, he found, is a product of development and the state’s presence rather than its absence. And so, the mule—more than any other animal the product of both intervention and development—is a material witness of violence and race in Guerrero.

By the time Vicente Guerrero began leading his mule trains against the Spanish Empire, Latin America had the highest ratio of mules to people in the world, and mule culture was central to Afro-Indigenous life.

American mule culture initially followed the ebbs and flows of mining profits. Though muleteering would become a self-sustaining aspect of Indigenous and afrodescendiente community and mobility, racism and the cost of mules were both prohibitive. The Spaniards held a monopoly on the mule trade and set restrictions on the exports of jacks (male donkeys) and mules to rival colonial powers. Mules were usually more expensive than horses in the colonial Americas despite their care being less capital-intensive, and most arrieros could not afford to own them. Instead, a rentier system tied arrieros to wealthy landowners and miners. Many colonial officials also prohibited both afrodescendiente and Indigenous communities from owning and using equines, but they could only control so much.

Blackness and ideas about blackness shaped muleteering. The direction of most knowledge transfer in the Americas went to afrodescendientes from Indigenous communities, who had generations of experiences with New World plants, animals, and climates. Mule culture, however, went the other direction.

African donkey husbandry is thousands of years old, which partially explains why colonial officials used African labor to work with livestock in the Americas. Similar racist thinking about a perceived African resistance to diseases, which Iberians weaponized to justify enslavement, was also adopted to force enslaved Africans into proximity with livestock. But this racist thinking was clumsy and stepped on its own toes. Like the marginal bits of plantation land ceded to enslaved people to grow their food, mule-related occupations became realms where enslaved people could emancipate themselves, if only in degrees. Moving products from plantations to ports and from communities to markets gave arrieros control of their time and food sources; it taught them how to live independently off the land and find shelter from the colonial state. As arrieros, the formerly enslaved could learn the landscape, build community, and even—as plotters against colonial government—free others.

Muleteering offered other kinds of mobility. In colonial Mexico, becoming an arriero was one of the ways formerly enslaved people moved up the “social pyramid.” This pathway was especially familiar in Veracruz and Guerrero, where plantation economies concentrated their racialized labor regimes. But the climb was as rocky and nonlinear as the mountains, full of gulches and ravines of racial prejudice.

The Latin word for mule (mulus) is the etymological root for “mulatto,” the term for a person of mixed Spanish and African ancestry in the colonial casta (caste) system, a hierarchical schema based on racial ancestry. The Spanish word for mule (mula) continues to carry negativity in Mexico today. As historian Isabelle Schuerch notes, 18th-century casta paintings offered visual cues to accompany ideas about racial mixings, including images of mules and muleteers in depictions of people of African descent.

When slavery and the colonial casta system were abolished after independence in 1821, the Mexican government rallied around mestizaje (mixed race of Spanish and Indigenous backgrounds) as a unifying national identity. Consequently, it stopped recognizing the distinction of being Mexican of African descent. Though racial animus toward the afrodescendiente community persisted, official acknowledgement of the community all but disappeared. Few official records of black presence in Mexico were created between 1829 and 2020, when Afro-Mexican advocates successfully lobbied to self-identify on census forms. Since Guerrero has the highest concentrations of afrodescendientes in Mexico, the loss of history was especially marked there.

The mule, an archive and material witness of empire and power, helps us fill that void. As such, we can analyze mules as proxies of the black experience in diaspora. They tread carefully, steady drivers of the history of race, empire, agriculture, and mining in Mexico, the U.S. South, and beyond.

Zora Neale Hurston famously asserts that “black women are the mules of the world.” In Joshua Bennett’s reading of Hurston’s collective works, he insists that “muleness moves through the text as an analytic of power.” Thinking with Hurston, Bennett brings forth that, as a “useful metonym for thinking about the nature of black social life,” mules and muleness can stand for both oppressive power as well as strength and resistance.

After a century of decline in black land ownership and farming, the promise of “40 acres and a mule” still resonates with black people trying to reconnect with the land. But what happens if we also reconnect with the mule? What can mules teach us about the black history of land and violence in the United States? Paralleling the history of arrieros in Mexico, the history of mules in the United States is as closely tied to mining and plantations as it is to black mobility and post-emancipation life. And, likewise, North American mules helped reestablish the same hierarchies of racism they slowly dismantled.

Along with racial categories, the mule gave industrialists a language for hybridity, which in turn influenced labor and scales of production.

In 1779 English inventor Samuel Crompton designed the spinning mule, a key innovation of the Industrial Revolution that enabled the mass production of high-quality yarn. Muleness inspired how Crompton combined two earlier yarn-making technologies: the spinning jenny, which spun multiple threads at once, and the water frame, which used rollers to draw out fibers. Crompton’s hybrid allowed a single operator to manage a large number of spindles simultaneously. Wide adoption of the spinning mule encouraged planters to cultivate more cotton, which in turn fueled demand for equine mule power on cotton plantations.

The mules that eventually populated the southern cotton plantation initially came from New England by way of Spain. As a cluster of British colonies, New England served as a breeding ground for horses destined for British sugar plantations in the Caribbean. While Spain had restricted trade to British colonies for generations, after the Revolutionary War the king of Spain presented President George Washington a prize jack named Royal Gift, whose offspring revolutionized labor in the United States and earned Washington the title “Father of the American Mule.”

Washington envisioned mule culture propagating across the United States, but mules gained the most traction in the plantation landscapes. As the legal slave trade came to a close in the early 19th century and demand for alternative sources of labor soared, New England farmers increasingly bred mules for export to the Caribbean and the U.S. South.

The changeover wasn’t immediate. For well into the 19th century, U.S. historical records seem to reveal more references to spinning mules than actual mules, but between 1850 and 1860 mule populations in the Deep South jumped from 266,000 to 529,000.

On January 16, 1865, four days after discussing the question of emancipation with 20 black ministers in Savannah, Union General William Tecumseh Sherman issued his Special Field Order No. 15 to begin redistributing confiscated land in 40-acre increments to the thousands of formerly enslaved people following his army’s triumphant March to the Sea. A subsequent order authorized the army to loan mules to the emancipated farmers. Together, these directives are the likely origin of the unfulfilled promise of “40 acres and a mule.”

How did mules become a symbol of emancipation for black folks so quickly? The short answer is cotton. Of all the mule varieties—sugar mules, mining mules, draft mules, pack mules—cotton mules were the most common. The longer answer is racism. Mules teach us about both whiteness and blackness in the United States, too.

Historian George Ellenberg insists there was nothing particularly romantic about the bond between mules and black farmers, enslaved and otherwise. Love and hate defined the relationship. White supremacy was an enthusiastic matchmaker, suggesting how mule power and black power complemented each other. This arrangement equated horses with authority, power, and overseers. Riding and driving mules was a black job.

 Coupling mule culture and black labor produced more white profits and power than black freedom. In 1856 the widely read magazine Southern Cultivator published another installment of a running debate, “Mule Power vs. Negro Power—Again.” Most planters agreed mules “attend to all necessary improvements on the plantations” and that there was money to be made in breeding mules, but planters fought over how much could be gained. In response to suggestions to expand plowing, one author asked: “Can a mule pick cotton? If not, what would it profit us to cultivate the whole world and lose it? . . . Does not the [field] hand have to follow the mule?” They believed that a “mule power system” would be more favorable “if we had machinery to gather [cotton] instead of the fingers.”

Like the Mexican arriero, black farmers gained some degree of social mobility on the backs of mules. They were a key resource in the Black Reconstruction. Before the Tuskegee Institute had land or money, it had a mule. It was Tuskegee’s first donation. The school’s Jesup Agricultural Wagon, drawn by a pair of mules, was a symbol of black progress. According to Jarvis McGinnis, the author of the Afterlives of the Plantation, George Washington Carver used the Jesup Wagon to make a traveling library that carried agricultural books and lessons from Tuskegee to black farmers across Alabama.

Mule ownership could offer a tenant farmer greater freedom to select among row crops. A large mule also consumes about three-fifths of the food a horse needs to perform the same labor. But despite being cheaper to keep than horses, mule ownership was beyond the reach of most black farmers. Like black arrieros, most could only afford to rent their mules, which could quickly become liabilities and debt. By the time the mechanical harvester began to replace black sharecroppers in the 1930s, the South’s mule population had peaked at around 6 million and was in decline itself due to other labor-saving technologies: tractors and trucks.

Mule power helped industry imagine what machine power could be. Mule culture, however, spread unevenly around the world. Equine mules are so rare in Britain that when English farmers talk of mules, they’re likely referring to a hybrid sheep. The absence of mule culture followed the English empire into the Americas; the Spanish monopoly on mules meant few worked colonial plantations in the Caribbean or British North America. In marketing his steam engine to the muleless English territories, James Watt was strategic about comparing engine power to the country’s more relatable and treasured animal. Had Watt been Spanish or Portuguese, we could have had engines measured in mulepower.

One horse does not equal one unit of horsepower. Horsepower, a measurement Watt defined in 1782, refers to the sustained output of an engine. In time and weight, this quantified horsepower as “the amount of work required from a horse to pull 150 pounds out of a 220-foot-deep hole or mine shaft.” The maximum output a horse can produce is about 15 horsepower, but over a day, the average production of a draft horse is approximately one horsepower. Engines evolved around the concept of horsepower, but in practice, they often coexisted with mules. Even as innovation expanded the energy sources engines could harness, many remained tethered to mule power.

Mules carried many of the engines designed to replace them. Some engineers acknowledged this irony, building machines that could switch out horsepower by combustion for mule power by draft. On late-19th-century sugar plantations from Louisiana to Mauritius, gasoline-powered loaders like the Moline could easily swap in mule power with a quick adjustment of the hoisting rope. If gasoline was scarce or too expensive, a Moline operator could exchange its three-horsepower gas engine for a mule.

Mules also carried much of the burden in the uneven introduction of electric power during the early 20th century. Out west, mining companies conducted cost-benefit analyses to compare the cost of hauling coal with electric locomotives or mules. Over time, these calculations favored electricity, but the work of transitioning mountain mines to electricity relied on the sure-footedness of the mule and the environmental knowledge of the muleteer.

Borders changed, but the arrieros remained. Mexican muleteers and their pack mules were proven and enduring forms of power during the westward expansion of mining that followed the U.S.-Mexican War (1846–1848) and the transfer of 55% of Mexican territory to the United States. The U.S. Army celebrated the Spanish and Mexican mules in extensive reports but said less about the arrieros themselves. Despite their silence, the military showed respect through imitation, copying the design of arriero aparejos (packsaddles). And because Baja and Alta California had sizable Afro-Mexican populations in the 1840s, including Afro-Mexican governor Pío Pico up north, arrieros of African descent surely traversed the region and were among those who supplied the men and machines that waged war against Indigenous populations and opened access to the region’s silver and copper.

Mule power and arrieros carried horsepower up mountains and brought ore and timber back down. As equipment got heavier, engineers began developing a new class of machinery divided into sections that mules could manage. According to an Industrial Progress article from 1909, “The development of mining and milling in the remote regions of the Rocky Mountains . . . and isolated mountain districts of Asia, Africa, and Australia, has been made possible only by the introduction of sectional machinery for mule-back and man-back transportation.”

Imagine a 40,000-pound Corliss engine, portioned into more than a hundred 375-pound sections, manufactured for a mining company in Mexico—its manufacturer crafting each piece according to the number of arrieros in the area, local environmental conditions, and the strength and seasoning of local mules. A mule has to work up to that kind of dense and unforgiving weight. Volume and mass change how weight feels. Three hundred and seventy pounds of compact metal pressed on the body can tear flesh in ways that the same weight of foodstuff won’t.

Then there’s length. In the case of loads engineers couldn’t divide, an arriero would have to align multiple mules safely and securely. It might take 12 mules to carry a 2,300-foot-long, ⅞-inch cable; 26 mules for a 1-inch cable of the same length. Bringing even moderate amounts of timber down a mountainside could take thousands of mule hours.

According to William Faulkner, mules eventually get their lick in for being so overburdened. A mule, he wrote, “will labor ten years willingly and patiently for you, for the privilege of kicking you once.” But many mining mules never got their retribution. After 16 months of moving 2,500 tons of material 5 to 6 hours a day, one company reported 38 mules had died.

Some companies believed mule transportation was too scientific to “be left to the [local] arriero,” but arrieros, in turn, also questioned the producers of sectional machinery and the businessmen who wanted it moved. It was not uncommon for arrieros to flat-out reject moving equipment that was too cumbersome. An article in a 1909 issue of Mining and Scientific Press acknowledged that “A good arriero will almost instinctively select the load best suited to the mule, and will also balance the load perfectly.” But that same good arriero might also “absolutely refuse[d] at any price” packages that were too heavy or destinations too dangerous to reach. Some observers believed muleteers could be as stubborn as mules. But like the mule, arrieros stubbornness could also be a calculated resistance that reflected intelligence and experience.

The historical record rarely captures arriero knowledge or how they felt, but we can see in business complaints that arrieros were known to leave troublesome carga “scattered along the trail.” Empire doesn’t always win.