The US-Mexico border winds its way for 2,000 miles from the Atlantic to the Pacific, tracking major rivers, crossing hills; deserts; and sprawling urban settlements. Regarding length, it is only the ninth-longest in the world (half as long as the US-Canada border), yet it is the busiest border on the planet, with about a million crossings daily. It is also the only major border between a first-world (that is: rich, advanced, post-industrial) society and a substantially poorer, developing country (once classified as part of the so-called ‘third world’). Given the marked imbalance between Mexico and the US – in terms of both per capita income and national power – the border has, for more than a century, seen major flows of migration (north), as well as investment (south); and it has experienced the ups-and-downs of this highly unequal bilateral relationship (more of that anon).


It is also a relationship characterised by significant cultural contrasts: between a United States that traditionally saw itself as a white, European, predominantly Protestant nation; while Mexico, as a fusion of Spanish colonialism and indigenous (Aztec, Maya and other) civilizations, was and is ethnically distinct, as well as overwhelmingly Catholic.

President Trump’s campaign promise to build a border wall – and to make Mexico pay for it – is but the latest episode in a long litany of US-Mexican altercations which have not only shaped Mexican history but have also had a decisive ­– and, arguably, growing – impact on the US too.

A man walks along the border fence between the US and Mexico in the Anapra area of Ciudad Juárez, Mexico. (Photo by Chip Somodevilla/Getty Images)
A man walks along the border fence between the US and Mexico in the Anapra area of Ciudad Juárez, Mexico. (Photo by Chip Somodevilla/Getty Images)

The existing US-Mexico border

The current border was established in the wake of the Mexican-American War of 1846–48: a war engineered by US President Polk in order to incorporate Texas into the Union and extend US territorial control across the vast area of the American Southwest. It was, as another president (Ulysses S Grant, in office 1869–77) put it, “one of the most unjust ever waged by a stronger against a weaker nation” (Grant, a veteran of the war, was writing in 1885). Mexico lost more than half of its national territory and acquired an abiding suspicion of its mighty northern neighbour.

Since that traumatic experience, the US-Mexico bilateral relationship has experienced sharp ups-and-downs; but there have also been underlying continuities. Once scantily populated, the border has acquired towns, cities, industry, transport links, and profitable agribusiness. Cross-border trade and migration have burgeoned: northern Mexico and the south-western United States, from Texas to California, have been the pacemakers of their national economies.

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James K Polk, the 11th president of the United States from 1845 to 1849. (Photo by Time Life Pictures/Mansell/The LIFE Picture Collection/Getty Images)
James K Polk, the 11th president of the United States from 1845 to 1849. (Photo by Time Life Pictures/Mansell/The LIFE Picture Collection/Getty Images)

Peace and stability

Economic – and cultural – integration across the border has created a distinctive border economy (and society), with its common interests and lobbies. One consequence has been a growing mutual interest in stable relations (and, in the here-and-now, considerable scepticism regarding Trump’s proposed wall). And, if we review the long history of both the border and the broader bilateral relationship between the US and Mexico since 1848, it is not much the severity, as the absence, of serious conflict that is striking. There have been rumours of wars, but no major military conflict. Close economic collaboration dates back more than a century and forged ahead as a result of the Second World War and, again, the 1994 NAFTA agreement (which established a free trade zone embracing Mexico, the United States and Canada).

Successive cycles in US and Mexican politics – Progressivism in the 1900s; the New Deal in the 1930s; neoliberalism in the 1990s – have created common bases for US-Mexican détente; and even at times of crisis and dispute (during the Mexican Revolution of the 1910s and ‘20s, or again in the 1970s and ‘80s), interests on both sides of the border have worked, with success, to defuse tension and drown out strident calls for confrontation. If we compare this history with roughly comparable bilateral relationships, similarly characterised by sharp inequality; cultural contrasts; and memories of violent conflict (for example, Ireland and Britain; Poland and Russia; or Poland and Germany), the US-Mexico relationship, for all its ups-and-downs, has been relatively peaceful and stable, and disputes have usually been successfully managed and mitigated. I doubt that the ephemeral Trump presidency will subvert this historical pattern.

Towards the end of the third century BC, the First Emperor of China sought to make his new state immortal by shielding it with what would be the earliest predecessor to the Great Wall. (Photo by Jean-Luc PETIT/Gamma-Rapho via Getty Images)


This skeletal picture requires fleshing out, by way of tracing the ‘ups-and-downs’. After 1848, both states faced internal upheaval (in part caused by the war itself). In the US, the acquisition of vast new territories made the issue of slavery even more acute, thus helping to provoke the Civil War. In Mexico, the trauma of defeat and dismemberment polarised politics and brought to power a generation of radical reforming Liberals – who, in the 1860s, had to confront, and defeat, a French invasion. In both countries, two iconic leaders, tempered by war and committed to progressive programmes, forged a cross-border bond of mutual interest and sympathy: Abraham Lincoln and Benito Juárez. Though the pair never met, they shared – and they knew they shared – roughly similar progressive republican values. They were also united by a common geopolitical concern for and opposition to European (especially French) intervention in the Americas. Not for the first or last time, politics north and south of the Río Grande followed a roughly common rhythm.

Similarly, the late 19th-century witnessed a shift towards more conservative, pro-business policies: the so-called Gilded Age in the US and the authoritarian regime of Porfirio Díaz in Mexico (1876–1911). Díaz, governing with ruthless pragmatism, achieved order, stability and growth. For the first time, substantial US – and European – investment flowed into Mexico, funding railways, public works, and a buoyant export sector (mining, oil, tropical plantations). The US and Mexican economies were knitted together and the border states flourished. In Mexico, democratic and civic rights were sacrificed on the altar of economic growth. US diplomats and investors lauded Díaz’s wise statesmanship, while radical – ‘muckraking’ – American journalists denounced his despotism and applauded the brave efforts of Mexico’s opposition.

Benito Juárez, president of Mexico (1861–72), who forged a cross-border bond of mutual interest and sympathy with American president Abraham Lincoln. (Photo by Universal History Archive/Getty Images)
Benito Juárez, president of Mexico (1861–72), who "forged a cross-border bond of mutual interest and sympathy" with American president Abraham Lincoln. (Photo by Universal History Archive/Getty Images)

The Mexican Revolution

In 1910, as the reformist Progressive movement crested in the US, the Mexican Revolution broke out: a broad, decentralised, popular challenge to the aged Díaz and his sclerotic regime. Conspiracy theories to the contrary, the US did not decisively incite or abet the Revolution. But events in Mexico seriously affected American business; national security and border interests.

The US did not react with one mind. Vested interests, like the big oil companies, denounced revolutionary demagogy and favoured hawkish policies: outright American intervention or clear-cut support for reactionary forces in Mexico. Liberals – like President Woodrow Wilson (1913–21) – sought to steer the Revolution in a moderate democratic direction. American radicals, enjoying a brief boom, lent aid to their comrades south of the border. For a decade (1910–20), Mexico experienced serious upheaval and civil war, to the detriment of both US investments and border security. President Wilson – wisely – resisted calls for outright armed intervention; but he twice sent troops into Mexico: first, in a clumsy attempt to advance the Revolution, ordering the occupation of the Gulf port of Veracruz (1914); then, two years later, in response to a cross-border raid by Pancho Villa (1916), despatching a so-called ‘Punitive Expedition’ into northern Mexico, supposedly to eliminate the offending bushwacker/bandit.

The ‘Punitive Expedition’ did not prove very punitive. Villa eluded his pursuers who, after a year of fruitless pursuit, withdrew from Mexico (not least because the War in Europe was now the paramount concern of the US). These twin interventions had scant impact on the course of the Revolution, though they understandably reinforced Mexican fears of US aggression. More importantly, the US managed to ride out the challenge of the Revolution without becoming embroiled in a full-scale invasion (of the kind it had mounted in Cuba and the Philippines in the 1890s; Haiti in the 1910s; or Nicaragua in the 1920s).

JFK prepares to sign the Nuclear Test Ban Treaty with the Soviet Union. (Picture by Corbis/Getty Images)


By the 1920s Mexico had acquired a stable ‘revolutionary’ regime, committed to policies of land and labour reform; economic nationalism; and robust anticlericalism, all of which alarmed the US. Again, the US (now under right-wing Republican rule) oscillated between the stick and the carrot; between threats and conciliation. By the late 1920s, the latter – ‘dove-ish’ – approach prevailed, and the Mexican leadership responded by moderating its policies towards the church and the foreign oil companies, thus promoting détente.

Détente was further favoured by the Great Depression, when politics in both countries lurched to the Left (with FDR and the New Deal in the US; and his Mexican counterpart, Lázaro Cárdenas (1934–40), the last great radical reformer of the Revolution). Loosely shared domestic agendas combined with threatening global circumstances to deepen US-Mexican détente. During the Second World War the US and Mexico achieved an unprecedented degree of bilateral cooperation, economic and military. This new, close – even cosy – relationship was further cemented by the Cold War. Mass Mexican migration to the US, officially sanctioned by the wartime bracero programme (1942–64), became a permanent feature of the North American political economy.

A portrait of George Washington. (Image by Getty Images)

Pragmatism trumps extremism

The US-Mexican relationship thus survived the serious challenge of the 1910 Revolution remarkably well. (We could contrast the sharp and enduring rupture provoked by the Cuban Revolution of 1959). Over time, on both sides of the border, pragmatism trumped extremism. The Mexican revolutionary leadership, though radical and nationalist, never aspired to Communism, while the substantial American economic interests in Mexico and along the border tended to favour pragmatic engagement.

The resulting détente endured through the post-war era. Bilateral issues – concerning migration; border water supply; and rules of investment in Mexico – proved manageable. More serious spats occurred in the 1970s, when Mexico briefly pursued more radical policies both at home and abroad; and, again, in the 1980s, when the Mexican economy tanked and political instability mounted. But these were passing storms. In the 1990s we again saw renewed US-Mexican collaboration, based on broadly shared political agendas (roughly, a ‘neo-liberal’ commitment to open markets and the free movement of goods and capital, though not of labour). NAFTA – the North American Free Trade Agreement (which came into force in 1994) – consolidated and deepened this collaboration. Even the newly salient issue of the 2000s – the boom in Mexican drug exports to the US, and the resulting spiral of violence south of the border – was, in a sense, a tribute to the intimate economic integration signalled by NAFTA.

Are we returning to an age of political extremes? (Illustration by Davide Bonazzi for BBC World Histories Magazine)

Trump’s wall

And so we return to Trump. During his presidential campaign, Trump repeatedly advocated building a wall along the entire US-Mexican border and making Mexico pay for it. The wall, Trump maintains, will hermetically seal the border, keeping out what he sees as murderers, drug-dealers and terrorists.

Now, as in 2016, the big "beautiful wall" is an electoral ploy, a device – like many Trump policies – to ‘rally the base’. It offers a non-solution to a misconceived problem. It is a non-solution because it will not effectively seal the border: the flow of drugs will continue while American demand remains insatiable. And the problem is misconceived because the ‘crisis’ of illegal Mexican immigration is largely a thing of the past: such immigration has fallen dramatically in the past decade, and there are more than one million fewer undocumented (note, not illegal) Mexican migrants in the US than there were a decade ago. However, greater numbers of Central American asylum-seekers, fleeing violence at home, now risk the hazardous journey through Mexico to the US border (where the majority are denied entry); it is this new phenomenon which fuels Trump’s populist hyperbole, while creating serious domestic problems for Mexico.

Lázaro Cárdenas, Mexico's left-wing president who in 1940 legalised drugs. (Photo by Henry Guttmann/Hulton Archive/Getty Images)

Within the great sweep of history, Donald Trump is seriously out of step. Historically, the US and Mexico have broadly got along, arguably to mutual advantage; even during the upheaval of the Revolution, conflict was managed, and war was averted. Trump now seeks to create a ‘crisis’ where none exists. In the US, powerful vested interests (business; border lobbies; migrant communities) are forces for restraint and conciliation. For this reason, Trump’s cavalier call to tear up NAFTA went largely unheeded. (NAFTA underwent a moderate facelift).

However, Trump’s Mexico-bashing did produce a predictable backlash south of the border: in the 2018 presidential elections the incumbent PRI (Partido Revolucionario Institucional) – seen as too soft on Trump – was humiliated and the leftist nationalist Andrés López Obrador won a decisive victory.


Alan Knight was professor of the history of Latin America at the University of Oxford from 1992 to 2013, when he retired.