River and Rock, Church and Gun

By Ben Stahnke

A Political Ecology of Expulsion, Racism, and Violence in the US-Mexico Border Region

A political border is both an idea and a material phenomenon: for those who live in their shadow, this fact can be observed both in the physical barriers—the looming walls, the militarized security, and the razor wire—and in the impact that such an imposing physicality has upon one’s daily life. In Walled States, Waning Sovereignty, political scientist Wendy Brown observed that, “nation-state walling responds in part to psychic fantasies, anxieties, and wishes and does so by generating visual effects and a national imaginary apart from what walls purport to ‘do.’”[1] Fortified political borders—border walls—both shape and respond to not only the material conditions of a nation-state, but to ideological structures as well. In Border People: Life and Society in the U.S.-Mexico Borderlands, border historian Oscar J. Martinez noted that, “borderlands live in a unique human environment shaped by physical distance from central areas and constant exposure to transnational processes.”[2] For the residents of a borderland, the border dominates one’s immediate physical life, as well as the thoughts experienced about such a life; yet the shadow of a border region looms large—over the history as well as the contemporary politics of the region.

In the United States in 2019, the current administration rose to power—in part—on the promise of a large-scale and militarized border wall along the 1,954 miles of the nation’s southern border; a wall designed to stem the northward flow of migration; a wall to separate the have-nots from the haves. The right-wing president Trump ham-handedly exclaimed that, “[t]his barrier is absolutely critical to border security. It’s also what our professionals at the border want and need. This is just common sense.”[3] But, to a critical eye, the so-called common sense of politicking is never quite what it appears to be at face value. The common sense of rightism is, in this case, a xenophobia made manifest in a policy strategy. It is a response to a rapidly changing world—both climatologically and geopolitically. And it is, as Ian Angus noted in Facing the Anthropocene, “a call for the use of armed force against starving people.”[4]

In Planning Across Borders in a Climate of Change, Michael Neuman noted that, "borders are always dynamic, ever shifting. Borders are human constructs enshrined in laws, treaties, regulations, strategies, policies, plans, and so on. We draft them, modify them and erase them at our will. We create, and recreate them, and cannot escape them.”[5] Yet, borders are not simply political in nature; they are economic as well. And these political economic phenomena have a history which is important. Under capitalism, borders are uniquely capitalistic; their logistical and material functions directed not only by security and military interests, but by banking, trade, and distribution interests as well. The 2011 publication of the World Bank, Border Management Modernization, defined a border as:

"...the limit of two countries’ sovereignties—or the limit beyond which the sovereignty of one no longer applies. The border, if on land, separates two countries. Crossing the border means that persons, and goods must comply with the laws of the exit country and—if immediately contiguous—the entry country. [...] Borders are not holistic. Different processes can take place at different places. For example, a truck’s driver may be cleared by immigration at the border, but the goods transported in the truck may be cleared at an inland location. Borders then essentially become institution-based and are no longer geographic."[6]

As intricate complexes of geographical, institutional, and administrational factors, borders are thus managed, maintained, and reformed by a host of political and economic forces. However, as the sociologist Timothy Dunn observed in The Militarization of the U.S.—Mexico Border, “Such issues are too important to be left to the discretion of bureaucratic and policy-making elites, or to be defined by jingoistic demagogues, who scapegoat vulnerable groups.”[7] Under capitalism, and along the southern United States border in particular, the erection of fortifications along the border delineation are entirely swayed by such jingoistic demagoguery.

As the World Bank’s Border Management Modernization argued, “inefficient border management deters foreign investment and creates opportunities for administrative corruption.”[8] Under capitalism, and under the aegis of jingoistic, racist, and conservative policies following the spirit of a new global Manifest Destiny, an inefficiently-managed border equates to a loss of potential profit: an unthinkable evil where capitalism’s logic of profit über alles prevails. And as Tim Marshall observed in The Age of Walls, “[w]alls tell us much about international politics, but the anxieties they represent transcend the nation-state boundaries on which they sit [...] President Trump’s proposed wall along the US-Mexico border is intended to stem the flow of migrants from the south, but it also taps into a wider fear many of its supporters feel about changing demographies.”[9] The land currently identified as the Mexico-United States border has seen, over time, its share of shifting demographies. The national anxieties and fears which presently add the requisite degree of legitimation to the Mexico-United States border wall are, in truth, the fears of a white settler—a stranger upon a land to which he does not belong.


The present-day Mexico-United States borderland was not always defined by the administrational and jurisdictional limits of the Mexican and American nation-states. In truth, the region has been well-populated since at least the onset of the Younger Dryas and the Last Glacial Period—and human habitation has been suggested in the southern region of North America for at least 18,500 years. The historian Paul Ganster noted that the region itself, “has a human history stretching back approximately twelve thousand years. The Americas in 1492 are estimated to have had a population of 60 million; 21 million, or 35 percent, of this total are thought to have lived in Mexico.”[10] The imposition of the present day border region of Mexico and the United States fractured—both geographically and socially—a landscape and peoples for whom no such fracture previously existed. Despite the mythos, colonization did not—in almost every instance—occur in wild, unsettled lands, but in lands abundant with inhabitants. The very essence of colonialism is at once bound up in a logic of displacement, genocide, and denial.

In Border Visions: Mexican cultures of the Southwest United States, anthropologist Carlos Vélez-Ibáñez noted that it was “highly likely that major parts of Northern Greater Southwest were well populated at the time of Spanish expansion in the sixteenth century,”[11] with the inhabitants of the region occupying socially and economically complex “permanent villages and urbanized towns with platform mounds, ball courts, irrigation systems, altars, and earth pyramids.”[12] Vélez-Ibáñez went on to note that, “at the time of [Spanish] conquest, the region was not an empty physical space bereft of human populations but an area with more than likely a lively interactive system of ‘chiefdom’-like centers or rancherías, each with its own cazadores (hunters), material inventions, and exchange systems.”[13] The majority of the pre-conquest inhabitants of the region were, according to Paul Ganster:

"what early Spanish explorers termed ranchería people, those who lived in small hamlets with populations only a few hundred each. Such settlements, often scattered over large surrounding territories, relied on wild foods as much as on planted crops. Where favorable agricultural conditions permitted, larger villages and more densely settled subregions existed. [...] Along the Rio Grande an estimated forty thousand people, practicing intensive agriculture, lived in highly organized villages."[14]

The notion that European colonization and settlement occurred in a depopulated wilderness is, as mentioned, naught but a myth of settlement—an ahistorical tool of legitimation for the children of settlers. In the much-lauded Changes in the Land, historian William Cronon observed that, “It is tempting to believe that when Europeans arrived in the New World they confronted Virgin Land, the Forest Primeval, a wilderness which had existed for eons uninfluenced by human hands. Nothing could be further from the truth.”[15]

The story of the pre-conquest border region is, as is the story of all of the Americas, one of violent displacement, of harsh and rapid resource extraction, and of pillage. In Open Veins of Latin America: Five Centuries of the Pillage of a Continent, Eduardo Galeano lamented that:

"Latin America is the region of open veins. Everything, from the discovery until our times, has always been transmuted into European—or later United States—capital, and as such has accumulated in distant centers of power. Everything: the soil, its fruits and its mineral-rich depths, the people and their capacity to work and to consume, natural resources and human resources. Production methods and class structure have been successively determined from outside for each area by meshing it into the universal gearbox of capitalism."[16]

The indigenous peoples of the Mexico-United States border region lived, and still live—along the border region’s western half—in the warmth and the aridity of the High Sonoran Region; an area characterized by:

"...high aridity and high temperatures. Typically, about half of the eastern part of the region’s precipitation falls in the summer months, associated with the North American monsoon, while the majority of annual precipitation in the Californias falls between November and March. The region is subject to both significant inter-annual and multi-decadal variability in precipitation. This variability, associated with ENSO, has driven droughts and foods and challenged hydrological planning in the region."[17]

The area itself is also mountainous—“criss-crossed by a maze of inhospitable ranges that divide the area into isolated subregions.”[18] Further, according to the Commission for Environmental Cooperation (CEC), and by way of the U.S. Environmental Protection Agency’s (EPA) Ecological Restoration in the U.S.-Mexico Border Region report, the present day border region is itself home to no fewer than seven unique ecosystems: the Californian Coastal Sage, Chaparral, and Oak Woodlands, the Sonoran Desert, the Madrean Archipelago, the Chihuahuan Desert, the Edwards Plateau, the Southern Texas Plains, and the Western Gulf Coastal Plain.[19]

While the Mexico-U.S. border region now is a “place where two historical-cultural tectonic plates are grinding against each other,”[20] it is a region whose delineations and delimitations have only been imposed recently: a “result of the Treaty of Guadalupe Hidalgo in 1848, [which] has never changed location except for the modifications introduced by the Gadsden Purchase of 1853 and one small sliver of land called ‘El Chamizal’ just north of the Rio Grande in El Paso that was set aside in 1963.”[21] Prior, however, to the American and Mexican treaties, and prior to the delimitation of the present-day border region, the area was home not only to indigenous peoples, but also to Spanish colonial aspirations.


Beginning with the 1492 journey of Christopher Columbus—a man who, on that very same 1492 journey, observed that, “[o]ne who has gold does as he wills in the world, and it even sends souls to Paradise”[22]; an insightful comment on the journey’s primary motivations—the resultant Spanish conquest of the Americas over the next several centuries was no less than a systematic genocide.[23] The indigenous peoples of the Americas suffered greatly under Spanish colonialism, and “[i]n little more than a century,” the economist and historian Michel Beaud observed, “the Indian population was reduced by 90 percent in Mexico (where the population fell from 25 million to 1.5 million), and by 95 percent in Peru. Las Casas estimated that between 1495 and 1503 more than 3 million people disappeared from the islands of the New World. They were slain in wars, sent to Castile as slaves, or consumed in the mines and other labors.”[24] The Council of Castile, “resolved to take possession of a land whose inhabitants were unable to defend themselves,”[25] and the wealth of the Spanish nobility increased exponentially—the cost being—both simply and brutally—genocide, slavery, and the rapacious extraction of resources. At its heart, the Spanish colonial impetus was one dominated by themes of greed, oppression, theft, murder, personal ennoblement, and of continued, relentless conquest. Virtually every colonial effort from the era seems to be dominated by these themes. Paul Ganster noted that:

"In the five decades after Columbus, the Spanish made a series of expeditions: Juan Ponce de Leon’s 1513 expedition to Florida; Alonso Alvarez de Pineda’s 1519 voyage around the Gulf of Mexico; Estevao de Gomes’s 1524-1525 recorrido (trip) up the northeastern seaboard; Pedro de Quejo’s 1525 voyage from Espanola to Delaware; Hernando de Soto’s 1539-1543 visit to what is today Florida and the Atlantic Southeast; and Joao Ridrigues Cabrilho’s 1542-1543 expedition along the California coast."[26]

The Spanish colonial expeditions had as their goal the procurement of wealth for the Spanish crown, as well as the securement of lands in the New World under Spanish sovereignty. “The production of sugarcane for rum, molasses, and sugar, the trade in black slaves, and the extraction of precious metals established considerable sources of wealth for Spain throughout the sixteenth century.”[27] For the Spanish, this growing wealth—following on the heels of the dominance of a growing territory—only fed the desire for more wealth; and where the “wealth of the kingdom depended upon the wealth of the merchants and manufacturers,”[28] there followed the insatiable growth of the Spanish conquest in and among the Americas.

Spanish conquest secured, for the monarchs of Castile, a vast majority of the land in the Americas, and, at its height, governance was divided amongst several viceroyalties—the Viceroyalty of New Spain, the Viceroyalty of Peru, the Viceroyalty of New Granada, and the Viceroyalty of Rio de la Plata. The viceroyalties, with their capitals centered in such present day metropoles as Mexico City, Lima, Bogotá, and Buenos Aires, were subject to the dictates and whims of the monarchs of Castile, where:

"...king[s] possessed not only the sovereign right but the property rights; he was the absolute proprietor, the sole political head of his American dominions. Every privilege and position, economic political, or religious came from him. It was on this basis that the conquest, occupation, and government of the [Spanish] New World was achieved."[29]

In the era of European empire, nascent capitalism, and the carving up of the world by the dominant European powers—expressions of both rapaciousness and technological might—monarchical whims became increasingly protectionist. “As other European powers became interested in the [present-day border] region and Spain’s interest in protecting its empire grew, the Far North was increasingly the focus of attempts to impede intrusions. Defense against the spreading influence of the French, English, and Russians became one of the main foundations of settlement.”[30]


Where late Spanish feudalism was still heavily dominated by the sphere of influence of the Catholic Church—a vestige of the ancient Roman imperialism, enamored with imperialism’s political logics of expansion and accumulation—there both went, hand-in-hand, upon the American landscape in the form of the northward settlements. Where the Spanish conquest of the Americas was concerned, both military and church acted in strategic coordination to secure lands and resources for the Crown. On this, Paul Ganster observed that, “[i]n order to pacify and populate the area at minimal cost, the Crown came to rely on two institutions with funds and personnel of their own: the military and the religious orders. This approach gave rise to the classic duo of European settlement in the North: the presidio and the mission.” Here, the unification of Christianity and the gun, of religious and militaristic dominance, emblematized the dialectic of late feudal political dominance—and it grew steadily northward upon the arid landscapes of what would later become the southern United States.

Over time, many of the early presidios— walled, defensible towns peopled by soldiers, officers and their families—grew to become permanent towns, and gradually, “warfare against raiding natives gave way to campaigns by new settlers and the government to distribute food and supplies to indigenous populations.”[31] Similarly, and alongside the presidios, the missions grew northward—the slow, insidious creep of European settlement seeped into abutting indigenous communities—and within a hundred years of Spanish conquest, “a string of missions stitched from east to west, cross the frontier and up the Pacific coast from Sinaloa to California.”[32] Alongside the presidios, the missions were also “expected to help pacify and incorporate Native Americans; they reduced into settled units the diverse and complex populations, particularly those who were semisedentary or nomadic.”[33] Thus both soldier and priest worked to settle the northern Spanish frontier in ways which were violent, politically recuperative, and emblematic of late-feudal/early-capitalist European colonization the world over.

However, soldier and priest alone did not colonize and subjugate the American frontera. Another, arguably stronger force followed in their shadow: the civilian settler. During the colonial period of 1492-1832, an estimated 2 million Spanish citizens flocked to the Americas to both colonize and settle the land. “Closely behind the Jesuits,” historian Samuel Truett observed, “came Spanish miners, merchants and ranchers. [...] Yet there was more to these migrations than the lure of profit, for Crown officials expected miners, merchants, and ranchers to defend as well as transform space. To hold the borders of the body politic, whether against Indians or other empires, colonists also went north as civilian warriors, with gun in hand.”[34] Civilian settlers—greater in number than the soldier of the presidio or the padre of the mission—came at first from Spain, and then Mexico City. But gradually, however, “immigrants were drawn from adjacent provinces. Sinaloa supply colonists for Sonora and Baja California, and these in turn supplied settlers for Alta California.”[35] As Paul Ganster noted, two distinct characteristics made these new Spanish frontier populations unique: racial diversity and the growing prevalence of wage labor.

"The inhabitants were of varied and mixed ethnicities, including Native Americans from all over the North and from central Mexico, as well as African Americans. Frontier society was also characterized by the prevalence of wage labor, which spread from the mines and urban settlements to agricultural areas, as a result of the high return on investment in the region, the need for skilled labor, and the location of the mining towns in areas of sparse indigenous population."[36]

By the mid-1700s, however, Spain’s northward expansion of the church and the gun, of presidio and mission, and of capitalist wage labor and colonial settlement began to wane. “Practical frontiers had to be drawn, and the imperial emphasis shifted from northward expansion to defend and consolidation.”[37] The unification of humans and nature, and the transformation of native American nature into something resembling European manorial economy was, in part, the mission of the mission; where, for the Jesuits, “the incorporation of humans and nature were part of the same equation. To attract converts and build mission economy, they sought to transform Sonora into a world of pastures and fields.”[38] Such efforts, however, were not only stymied by native populations unaccustomed to such an economy, but by nature itself. “Often,” noted Truett, “natural disorder followed in the wake of social disorder.”[39] Social, political, and environmental pressures all lent themselves to the halting of Spain’s northward movement, and, with the onset of the nineteenth century, an increasing friction between the New Spain and the Old, and the Napoleonic invasion of the Iberian peninsula, New Spain soon declared its independence from the Old.


Mexican independence from Spain, and the slow emergence of the present day Mexico-United Stated border delimitation, did not occur all at once; but through an overdetermination of historical, political, and economic factors. The geographer Joseph Nevins noted that:

"The origins of the U.S.-Mexico boundary are to be found in the imperial competition between Spain, France, and England for ‘possessions’ in North America. The Treaty of Paris of 1783, which marked the end of the American war for independence, resulted in the United States inheriting the boundaries established by its English colonial overseer. [...] The Treaty of Paris thus resulted in a situation where the United States shared its southern and western boundaries with Spain."[40]

New Spain qua the newly-independent nation of Mexico similarly found its borders shifting in the tumult of the nineteenth century. Independence brought with it a removal of the sovereignty of the Spanish Crown, but also a new type of vassalage to France, for whom it became, essentially a client state.[41] The eyes of the United States soon turned to Sonora, and “[b]y the time Americans began to dream of Sonora, Sonora was a dream that had traveled across national borders, halfway around the world, and back again.”[42] Capitalist interest in the rich Sonoran region—inextricably entangled with Europe’s settler colonial interests in the New World—continued unabated, and shifting borders, losses of heretofore sovereign interests, and a geography in flux all presented themselves as ripe fruits for the capitalist interest. Historian Samuel Truett observed that the German geographer Alexander von Humboldt’s Political Essay on the Kingdom of New Spain, for example, “was translated into English in 1811 with the goal of luring European capital to Mexican mines. And the idea of unfinished conquests appealed to a British capitalist class that was beginning to invest energetically at home and abroad.”[43] Equally true of both the nineteenth century and the present day, nothing quite draws capitalist interest like political instability, exploitable economies, and the dream of so-called “opportunity” in the service of personal profit.

The 1821 independence of Mexico from Spain brought with it many new instabilities. Historian Rachel St. John noted that, “[t]erritorial competition defined North America in the early nineteenth century. At the beginning of the century, the continent was still very much up for grabs.”[44] And Samuel Truett noted that, “[w]ith independence in 1821, [Spanish] trade barriers were dissolved, to the great relief of entrepreneurs.”[45] For both the new nation of Mexico and the increasingly imperialistic United States, political upheavals, economies-in-waiting, and geographical instabilities became the driving themes of the nineteenth century in North America—particularly where the future Mexico-U.S. border region was concerned. Paul Ganster noted that, “During the relatively brief span from Mexican independence in 1821 to the end of the between the United States and Mexico in 1848, Spain’s far-northern frontier territories became borderlands—the relatively unrefined and frequently contested terrains between Mexico and the United States.”[46] Mexico’s recent independence, the machinations of empire, and the increasingly contested borderlands entailed by the Louisiana Purchase and Texas soon drove the United States and Mexico to war. On the Louisiana Purchase, Joseph Nevins noted that:

"Napoleon compelled Charles IV of Spain to cede an enormous territory west of the Mississippi River to France in 1800 in return for lands in Italy. [...] Three years later, however, Napoleon sold the vast territory to the United States for $15 million—an exchange known as the Louisiana Purchase—without taking Spanish opinion into consideration. [...] Almost immediately after the signing of the treaty, however, U.S. President Thomas Jefferson foreshadowed U.S. expansionist designs on Mexico, expressing the view that Louisiana included all lands north and east of the Rio Grande, thus laying claim to Spanish settlements such as San Antonio and Santa Fe."[47]

With the Louisiana Purchase nearly doubling the size of the young and land-hungry United States, questions and conflict of delimitation and boundary soon arose with the newly-independent Mexico. Historian Oscar Martínez noted that:

"With independence achieved in 1821, Mexico inherited from Spain the challenge of safe-guarding the vast northern frontier. More population was needed to strengthen the defenses of California and Texas particularly. Following policies begun by Spain, Mexico in the 1820s allowed entry into Texas of large numbers of immigrants from the United States in order to further populate that sparsely settled province. [...] Within a short time Mexico would realize what a volatile situation it had unwittingly created within its own borders."[48]

With eastern and western Florida having already been acquired from Spain between 1795 and 1819, the Louisiana Purchase of 1803, and the cession of northern lands in Minnesota by Britain in 1818, the eyes of the United States gazed hungrily at the lands north of present-day Mexico in Texas, the now-southwestern states of Arizona, New Mexico, and California. These U.S. imperialist-expansionist efforts—efforts which emerged, ideologically, as the concept of Manifest Destiny—quickly brought the United States and Mexico to war. “Once the philosophy of Manifest Destiny took firm hold in the European American mind the outcome seemed clear: sooner or later the United States would detach and annex Mexico’s northern territories.”[49] In a now well-known strategy of American imperial-economic interventionism, the United States acted quickly to foment dissent in the northern Mexican territory; foreshadowing war and military annexation. Joseph Nevins observed that:

"In the aftermath of Mexican independence in 1821, U.S. economic actors exploited political instability in what today is the Southwest. Through their long-distance trade routes, the associated socio-cultural ties they engendered, and sponsorship of raids by Native groups against Mexican communities and Mexico’s emerging state apparatus, they helped to undermine those communities and the state."[50]

After the 1836 Texas declaration of independence from Mexico—an independence fed, largely, by American settlement in the region—and the eventual 1845 annexation of Texas by the United States, an annexation that faced popular approval by Texan “pro-slavery southerners,”[51] the doctrine of Manifest Destiny—the idea that “it would be beneficial to both countries to absorb Mexico into the United States”[52]—diplomatic relations between the United States and Mexico rapidly deteriorated and war loomed on the horizon. In the early part of 1846, U.S. President James Polk sent troops to the Rio Grande, hoping to provoke Mexico into war, and “to make Mexico recognize the Rio Grande as Texas’ southern boundary, and (perhaps most importantly) to face Mexico to cede California and New Mexico to the United States.”[53] War, by way of American provocation, of course did erupt, and the Mexican-American War—over a span of two years—claimed the lives of over 25,000 Mexicans and 13,500 Americans.

The war ended on February 2, 1848 with the signing of the treaty of Guadalupe Hidalgo—officially entitled the “Treaty of Peace, Friendship, Limits and Settlement between the United States of America and the Mexican Republic”—and the new southern border of the United States was set at the Rio Grande, with the additional land concession of the Gadsden Purchase in 1853 solidifying the current southern border of the United States. Historian Rachel St. John recorded that:

"With U.S. soldiers [in 1848] occupying the Mexican capital, a group of Mexican and American diplomats redrew the map of North America. In the east they chose a well-known geographic feature, the Rio Grande, settling a decade-old debate about Texas’s southern border and dividing the communities that had long lived along the river. In the west, they did something different; they drew a line across a map and conjured up an entirely new space where there had not been one before."[54]

The newly designated southern delimitation of the United States was, as all borders tend to be, an imaginary line with very real material consequences. The United States border severed communities and families from each other, arbitrarily divided homogenous ecosystems and species, and drew, essentially, a series of straight lines in the sand from El Paso and Ciudad Juárez to the Pacific Ocean. The historian Thomas Martin observed that:

"The United States pioneered the idea of the straight-line geometric border, based on surveying techniques that (bizarrely, if you think about it) use magnetism and the position of stars rather than the actual lay of the land or ethnic considerations. The habit was formed even before the Revolution, when the proprietors of Maryland and Pennsylvania hired the astronomers Charles Mason and Jeremiah Dixon to discover the exact boundary between their colonies."[55]

The straight-line approach to border delimitation occurred, in 1848, by “U.S. and Mexican officials [...] simply drawing straight lines between a few geographically important points on a map—El Paso, the Gila River, the junction of the Colorado and Gila rivers, and San Diego Bay.”[56] Importantly, the only “natural” boundary delimitation along the southern border of 1848the Gila River, was made obsolete and irrelevant by the 1853 Gadsden Treaty. The unique straight-line peculiarity of the western portion of the United States southern border would soon prove to provide numerable economic, political, and security consideration for the United States—considerations which still occur to this day.


Since 1848, the border management trend for the southern delimitation of the United States has taken on an increasingly violent character. Further, the primary subthemes of this violence have been racism, economism, protectionism, and militarism. As Joseph Nevins observed, “[i]t took many decades for the United States to pacify the area along its southern boundary, as part of a process of bringing ‘order’ and ‘civilization’ to a region perceived as one of lawlessness and chaos.”[57] For capitalism, order and civilization equate to the often violent and repressive impositions of federal authority. Rachel St. John noted that, “In the years following the boundary line’s creation, government agents would mark the desert border with monuments, cleared strips, and, eventually, fences to make it a more visible and controllable dividing line,”[58] a dividing line which “allowed the easy passage of some people, animals, and goods, while restricting the movement of others.”[59]

The Mexico-U.S. border in the second half of the nineteenth century was never quite a settled matter. The legal agreements between the governments of the United States and Mexico stood, yet many expansionist-minded Americans—the so-called filibusters—saw fit to make incursions into Mexican territory in an effort to establish new southern slave states for the United States—actions to which the United States often turned a blind eye. The filibustering incursions both preceded and followed the Mexican-American War, but, as Oscar Martínez observed:

"The years following the U.S.-Mexico War have been called the golden age of filibustering. Men seeking fortune or power cast their eyes on the resource-rich and thinly populated northern tier of Mexican states. War veterans, forty-niners, and miscellaneous travelers during the late 1840s and early 1850s had portrayed the region in colorful, exotic, and economically attractive terms."[60]

Martínez went on to observe that the early filibustering efforts—efforts and excursions which lasted well into the early part of the 1900s—constituted “a central part of U.S. expansionist aggression directed at Mexico. The periods of the greatest unlawful invasions organized in the United States coincide with weakness and instability in Mexico.”[61] The filibustering and pseudo-filibustering excursions added heavily to the distrust between Mexicans and European Americans, and it was not until the 1930s and 1940s that “fear [began] to dissipate south of the border”[62] of future filibuster incursions.

As a largely un-policed, heavily-contested, and volatile region for the bulk of the nineteenth century, the onset of the twentieth century saw an increasing trajectory of control along the United States’ southern border. In July 1882, the United States and Mexico formed “a new International Boundary Commission and charged it with resurveying and reaping the border, replacing monuments that had been displaced or destroyed, and adding monuments so that they would be no more than 8,000 meters apart in even the most isolated stretches of the border and closer in areas ‘inhabited or capable of habitation.’”[63]

The Mexican Revolution of 1910, violence, diplomatic disputes, and an economic instability which had disrupted the transborder economy, all led towards an increasing militarization of the Mexico-U.S. border in the early 1900s. Rachel St. John noted that the persistent smuggling of cattle, narcotics, and immigrants—all fallouts from the Mexican Revolution—led to the United States government’s (now-persistent) decision to dispatch troops to its southern boundary to “insure that revolutionaries did not access American arms or launch invasions from U.S. soil.”[64] The increasing militarization of the southern border was also, as noted by sociologist Timothy Dunn, “defined by efforts to maintain control over the flow of Mexican immigrant workers into the United States, typically in ways that also significantly affected Mexican Americans.”[65] Increasing control of the cross-border flow of migrants and goods—the “revolving door” immigration policy—led to the establishment in 1924 of the U.S. Border Patrol—by way of the Immigration Act legislation—as “the chief guardian of the ‘revolving door’ and the main agent of the comparatively less severe forms of border militarization carried out during ensuing decades.”[66] Historian Kelly Hernández observed that the newly-designated “Border Patrol officers—often landless, working-class white men—gained unique entry into the region’s principle system of social and economic relations by directing the violence of immigration law enforcement against the region’s primary labor force, Mexican migrant laborers.”[67]