The 51st State That Never Was: Why the United States Didn’t Annex Canada

Why didn’t the United States annex Canada during earlier historical periods? In short, because it didn’t want to.

President Donald Trump has drawn widespread criticism (dating back to before his first term) for seeing U.S. foreign policy in ways that reflect the international politics of the 19th century rather than the 21st century. There are many reasons for this — from his mercantilist economic perspective and readiness to raise tariffs to his devaluing of U.S. alliances and skepticism toward international institutions. Even more so, however, Trump has drawn attention at the start of his second term by repeatedly calling for U.S. territorial expansion into Greenland, Panama, and Canada.

After reportedly joking about annexing Canada during a late November dinner with Canadian Prime Minister Justin Trudeau, Trump drew headlines in December by describing Trudeau as “governor” of the “Great State of Canada.” By early January, he began suggesting to “get rid of” the U.S.-Canadian border, calling it an “artificially drawn line” and tweeting two images of maps showing Canada as part of the United States. Many observers initially declined to take such statements seriously, but Trump reiterated later in January, “I would love to see Canada become the 51st state” and he particularly raised eyebrows — and concerns — by including in his address during the World Economic Forum in Davos, “Canada … you could always become a state.”

Such rhetoric diverges sharply from every other U.S. president in living memory.

Since World War II, the prohibition of coercive territorial expansion has been a central feature of both international law and U.S. foreign policy. After President Woodrow Wilson first worked to outlaw conquest via the League of Nations, Presidents Franklin Roosevelt and Harry Truman made territorial integrity a central principle of the United Nations system. Ever since, the United States has led efforts to deter and punish would-be conquerors from Saddam Hussein to Vladimir Putin. Indeed, the understanding that the United States does not seek to dominate other countries is central to arguments that those countries should prefer its brand of international order over alternatives — whether led by the Soviet Union during the Cold War or potentially by China today.

Of course, the United States has its own notable history of territorial expansionism — including to its north. Yet that history neither offers precedent for Trump’s recent statements nor in any way directly informs them. Indeed, the history of U.S. territorial expansion is far more nuanced than is often remembered today. Its greatest lessons ultimately lie in understanding not why 19th-century U.S. policymakers sometimes tried to annex territory in what is now Canada, but why they never genuinely tried to make it the “51st state.”

Canada and U.S. Territorial Expansion

The history of U.S. northward expansionism goes back all the way to the Revolutionary War, but it would be wrong to suggest that U.S. policymakers have consistently or even frequently tried to annex Canada. In fact, if we define “the U.S. government” as the federal government under the U.S. Constitution and “Canada” as the entirety of modern Canada (as illustrated in Trump’s map memes), it would be wrong to suggest that the United States has ever genuinely tried to annex Canada. Instead, as I have explored at length in The Picky Eagle, U.S. policymakers between the 1780s and 1870s made periodic attempts to acquire relatively sparsely populated areas of what is today western Canada, but they generally rejected the notion of annexing the relatively populous British colonies in eastern Canada. Indeed, setting the soundbites aside, the history of U.S. northward expansionism is far more complex than we often remember.

U.S. policymakers’ eyes turned northward even before the Declaration of Independence, when the Continental Congress invited Quebec, St. John’s Island, and Nova Scotia to join its members in renegotiating their collective relationship with Britain. Quebec’s relatively large population offered the most significant additional leverage, so the Congress appealed to its people and authorized a land invasion during the winter of 1775–1776 to drive out British forces. That effort ended in a disastrous assault on Quebec City during a New Year’s Eve blizzard, which left Gen. Richard Montgomery dead and the remaining force under Benedict Arnold decimated, disease-ridden, and starving. While Commander-in-Chief George Washington recognized the geopolitical benefits of including Quebec and periodically considered new northward invasions throughout the Revolutionary War, he repeatedly dismissed the notion given the Continental Army’s struggles to secure the 13 states and his concerns that allied France — if included in a joint operation — might reassert its own claims to Canada (having lost it to Britain in 1763).

Even after securing independence from Britain, Article XI of the Articles of Confederation — in effect between 1781 and 1789 — extended an open-ended invitation: “Canada, acceding to this confederation, and joining in the measures of the United States, shall be admitted into, and entitled to, all the advantages of this union.” While this invitation would be an unusual feature for a national constitution, it makes more sense when considering that the articles created an alliance, not a unified nation-state: “a firm league of friendship” specifying that “each state retains its sovereignty.” Accordingly, the 13 states had nothing to lose and everything to gain from encouraging Quebec to cast off the British crown and join them. That changed when the U.S. Constitution merged their domestic politics under a shared federal government. Notably, the Constitution has never contained any such invitation for Canada to join. Instead, after 1789 federal policy began exhibiting a new expansionist pattern (both generally and toward Canada): pursuing more land rather than more people.

In 1812, the United States once again declared war on Britain and invaded Canada. Yet the War of 1812 was not a land grab. In fact, it marks an important case in U.S. foreign-policy history for precisely the opposite reason. The War of 1812 marked the first major occasion when U.S. policymakers declined to pursue a potentially profitable opportunity to annex neighboring territory. With Britain distracted by the Napoleonic Wars, expansionist policymakers might have prepared a robust military force capable of driving Britain off the North American continent once and for all and securing regional hegemony. Yet most historians of the war agree that annexing Canada was not the U.S. war aim. Indeed, neither President James Madison’s administration nor congressional leaders wanted to annex Canada. Instead, the War of 1812 was an episode of coercive bargaining. After years of British restrictions on U.S. trade and impressment of U.S. sailors into the Royal Navy during the Napoleonic Wars — and years of failed efforts to press Britain to repeal those restrictions via economic sanctions starting with President Thomas Jefferson’s embargo — war offered the last source of leverage over Britain, and Canada represented its most tangible weak spot. As I wrote in Diplomatic History, “The war was a desperate act on the part of U.S. leaders brought to their wits’ end by British maritime restrictions, which were themselves desperate acts by a British government fighting for its life against Napoleon.”

Far from genuinely trying to conquer Canada, Congress declared war with a woefully underprepared military, and the Madison administration lobbied the British for peace (with the maritime restrictions removed) as soon as war was declared. In a frequently misquoted soundbite, Secretary of State James Monroe wrote to U.S. chargé d’affaires in London Jonathan Russell that it might be “difficult to relinquish territory which had been conquered” — not as a secret confession of expansionist intent, but rather as a potential argument to convince Britain to back down on the maritime restrictions and avoid war altogether. Instead of coveting annexation, policymakers worried about its potential domestic consequences: how it might upset the emerging sectional balance of power between North and South, spark secessionist movements, and corrupt U.S. society by assimilating Quebec’s largely French and Catholic population (along with British loyalists who had fled north after the revolution). While a few congressmen from border areas did advocate expansionism, even they targeted sparsely populated areas north of the Great Lakes rather than the population centers of Quebec.

This east-west divide in U.S. northward expansionism, rooted in the interplay between democracy and xenophobia, hardened further during the decades that followed. Many know of President James Polk’s aggressive diplomacy over Oregon during the mid-1840s, which spawned slogans like “Fifty-Four Forty or Fight!” and “The only way to treat John Bull was to look him straight in the eye.” In 1818, the U.S.-Canadian border east of the Rocky Mountains had been set at 49° but the area west of the Rockies between Mexico (42°) and Russian Alaska (54°40’) remained under joint U.S.-British control. Polk chose confrontation, pressing U.S. claims to the entire region until June 1846, when news of British war preparations combined with Congress’ declaration of war against Mexico the previous month raised the specter of a two-front war and prompted him to settle for extending the 49° border to the Pacific.

Less widely remembered, however, are the lengths to which U.S. policymakers had gone only a few years earlier to avoid conflict in eastern Canada rather than pursue territorial expansion there. Beginning in November 1837, a rebellion in what is now Quebec and Ontario offered the first widespread evidence of Canadian dissatisfaction with British rule — a golden opportunity for any would-be expansionists below the border. Yet President Martin Van Buren chose to strictly enforce neutrality, ordering border states’ governors to prevent U.S. citizens from aiding the rebels. Even after British forces killed a U.S. citizen while storming the steamboat Caroline — the event that sparked Secretary of State Daniel Webster’s famous memo to his British counterpart elucidating the laws of war — Van Buren issued a neutrality proclamation and sent Gen. Winfield Scott to the border to suppress the spreading war fever rather than fan it in service of expansionism. Two years later, Maine’s governor John Fairfield offered another pretext for expansionism: In response to timber poaching in a disputed area between Maine and New Brunswick, he sent state militia north to occupy the area and requested federal support. Yet Van Buren immediately condemned Fairfield’s actions, and congressional leaders like Henry Clay refused to allow one state to “draw the entire Union, without their consent, into war with a foreign power,” empowering the president to rally 50,000 militiamen to ensure border stability by overwhelming both any Canadian belligerents and Maine’s own force.

The late 1860s offered another golden opportunity to outsource the costs of a northward invasion, this time to the Fenian Brotherhood (the U.S. branch of the precursor to the 20th-century Irish Republican Army), which stockpiled surplus arms and organized Irish-American veterans to invade Canada in hopes of gaining leverage to bargain for Irish independence. The Fenians enjoyed substantial popularity amid U.S. perceptions that Britain had favored the South during the Civil War, for example by supplying the Confederacy with the warship Alabama that had preyed on Union shipping. This time, moreover, the U.S. military was both large and experienced, drawing jealous appraisals from European powers due to its experience using modern technologies and strategies during the Civil War. Yet instead of promoting Canada’s annexation, President Andrew Johnson and Secretary of State William Henry Seward undercut the Fenian raids by seizing their weapons, reinforcing U.S. neutrality, and even transporting individuals home from the Canadian border at public expense after they promised not to engage in further raids. President Ulysses Grant continued this approach after assuming office in 1869.

In contrast, the same U.S. policymakers did pursue annexations in the vast, sparsely populated continental northwest, including Russian Alaska as well as British Columbia, Rupert’s Land, and the Hudson’s Bay Company’s North-Western Territories. Seward readily accepted Russia’s offer to sell Alaska for $7.2 million in March 1867, seeing it as useful to secure Russian friendship and to incentivize the subsequent annexation of British Columbia (now sandwiched between U.S. territories). Hoping to “pay for British Columbia with the Alabama claims,” Seward sought to rally public opinion toward favoring U.S. annexation among Vancouver’s residents (numbering less than 10,000). Britain’s eastern Canadian colonies effectively swayed public opinion toward deeper integration with themselves during the winter of 1867–1868, however, and Parliament’s commitment to build a transcontinental railroad that summer proved a more enticing offer. The Grant administration still held out hope of annexing western Canada during the 1869 Red River Rebellion among Winnipeg’s Métis population, maneuvering behind the scenes to keep the door open for a potential exchange of territory for the Alabama claims. The rebellion proved short-lived, however, and Britain pacified local concerns by instituting legal protections for the Métis.

With all plausible diplomatic pathways to further expansion in western Canada closed, the Grant administration formally abandoned any further northward territorial ambitions. Instead, it negotiated the 1871 Treaty of Washington resolving all major U.S.-British disputes — including not only the Alabama claims but also northeastern fishing rights, border waterways, and a boundary dispute over the San Juan Islands. British power remained a potential threat to U.S. interests, however, and Canada remained its most vulnerable pressure point. Accordingly, military planning for possible northward campaigns continued. In 1887, for example, a dispute over fishing rights prompted the U.S. Navy to survey Canada’s defenses and develop plans for a potential three-pronged campaign to conquer Canada should war break out. Even after fighting as allies in World War I, Britain remained uniquely capable of threatening the continental United States via its navy and control of Canada, so U.S. planners continued to take the prospect of a future U.S.-British war seriously during the 1920s and 1930s. Even as they considered it “highly improbable,” they worried that ongoing U.S. economic penetration into regions formerly dominated by Britain might prompt a British effort to eliminate that commercial threat, so they devised War Plan Red — which proved to be the last U.S. plan for potential war with Britain as their subsequent alliance during World War II and the Cold War rendered such planning obsolete.

Meanwhile, the notion of annexing Canada became a relatively transparent boogeyman within U.S. politics, revived only in service of other political agendas. While self-interested private actors occasionally advocated a voluntary annexation, the U.S., British, and Canadian governments all saw value in maintaining a stable and peaceful border. Indeed, the U.S.-Canadian border would be hailed as the world’s longest demilitarized border well into the 21st century.

As this history shows, U.S. policymakers between the 1770s and 1870s maintained regular interest in annexing sparsely populated areas of western Canada by diplomatic means if possible. While a hypothetical third U.S.-British war would likely have prompted another northward U.S. military campaign that may have resulted in the conquest of parts of what is now Canada, such counterfactual scenarios are ultimately unrealistic given that every president from 1815 through to the present has favored peace over northward territorial expansion (notably in contrast to Madison’s and Monroe’s salami tactics to annex Florida and Polk’s war with Mexico). Far more noteworthy are the limits on U.S. territorial ambitions: While various policymakers tried to acquire sparsely populated western areas, they also displayed an equally longstanding disinterest in annexing relatively populous eastern Canada. In doing so, they reversed the logic of many theories of great-power politics, which would predict sustained early efforts to absorb Quebec and drive Britain off the continent in order to secure regional dominance.

Finally, it is worth observing that despite U.S. policymakers’ disinterest in annexing Canada’s people, invasions from the south did play a major role in fueling the emergence of Canadian nationalism. The military campaigns during the Revolutionary War and the War of 1812 offered powerful historical touchstones for future narrators of Canadian nationalism, and the Fenian raids reignited security fears north of the border enough to fuel the 1867 consolidation of Quebec, Ontario, Nova Scotia, and New Brunswick into the Dominion of Canada (joined shortly thereafter by Manitoba and British Columbia). In this way, the prospect that the United States might annex Canada proved far more significant to the latter than the former.

The Implications of Trump’s Expansionist Rhetoric

For all Trump’s talk, the chances of the United States annexing Canada during his second term remain low. The Canadian public overwhelmingly opposes it (90 percent, according to a recent survey by the Angus Reid Institute) and the U.S. public does too. With no deal in sight, it is far more likely that Trump intends his expansionist rhetoric to unsettle the diplomatic status quo in service of other goals. As former senior adviser to Trudeau Gerald Butts remarked, “Trump used this ‘51st State’ line with Trudeau a lot during his first term. He’s doing it to rattle Canadian cages.”

This does not mean that Trump’s rhetoric is inconsequential — far from it. Trump’s talk of territorial expansion has already generated important consequences. Most notably, it has served up rhetorical ammunition to other revisionist powers, especially Russia. Beyond reasserting Russian interests in the Arctic (which both Canada and Greenland touch), Russian media figures have already used Trump’s statements to defend Russia’s ongoing invasion of Ukraine, even saying that “Trump’s position essentially gave Moscow the right to demand the restoration of its own former Soviet empire, including the Baltic nations of Estonia, Lithuania and Latvia.” Such whataboutism muddies the waters of international diplomacy in ways that erode the soft power derived from 75 years of strong U.S. support for the territorial integrity norm. Even as various aspects of U.S. foreign policy have sparked resistance — from Cold War interventions to the War on Terror — the United States has consistently attracted allies and partners in other regions in part because they know that they have less to fear from it than from their neighbors. The less distinguishable U.S. foreign policy becomes from Russian or Chinese foreign policy, the fewer reasons other countries have to favor U.S. interests over those of its geopolitical rivals.

Second, Trump’s expansionist rhetoric undermines U.S. national security by impairing its alliances and border security. Trump has long failed to understand NATO’s significance, threatening to withdraw the United States from the alliance during his first term. Any alliance is only as strong as the political will behind it, so Trump does not need to withdraw from NATO to fundamentally weaken it. How can U.S. allies count on someone to help defend them who refuses to rule out using force to conquer territory from one of those very allies? Diluting alliance cohesion weakens the United States by reducing the likelihood that its partners will offer their own support when it is needed — as they did after 9/11, the only time NATO’s Article 5 has ever been invoked.

Beyond its alliances, any military strategist or scholar of international relations will observe that the single greatest advantage the United States has over its geopolitical rivals is its geography: namely, stable continental borders that have facilitated relatively amicable relationships with its neighbors for more than a century. In Joseph Nye’s words, echoed by countless others: “The United States is surrounded by two oceans and two friendly neighbors, while China shares a border with fourteen other countries and is engaged in territorial disputes with several.” This results in vastly different force postures and capabilities. While China’s military is rapidly modernizing, much of its strength is deployed along its lengthy land borders with Russia and India. In contrast, the U.S. military can focus much of its attention on various overseas theaters precisely because the U.S.-Canadian border has been demilitarized for so long.

Third, Trump’s rhetoric intentionally disparages Canada’s sovereignty. Portraying Canada as on par with any of America’s 50 component parts rather than as a sovereign equal erodes another central principle of the current international order, harkening back to an age of European imperialism in which other countries were routinely denied recognition of their full sovereignty, often on racialized grounds. Furthermore, it is noteworthy that Canada is internally composed of 10 provinces and 3 territories, yet Trump has continuously spoken of it becoming “the 51st state” rather than raising the total number of U.S. states to 63. Doing so makes for a headline-grabbing soundbite and asserts a predominant U.S. bargaining position that Trump would surely like Canada to accept (though there is no sign it will do so).

Yet it is also instrumental. In the unlikely event that annexation comes to pass, Canada becoming the 51st state would give it only two seats within the U.S. Senate, minimizing the resulting gain in domestic political influence for whichever party Canadians are more likely to support (hint: not Trump’s). As I have examined at length in The Picky Eagle, such domestic costs profoundly shaped the pattern of U.S. territorial expansion, time after time offering the key reason why the United States refrained from pursuing more opportunities to expand than it did. The annexation of Texas, for example, was accompanied by a heated debate over whether to admit it as a single state or divide it into several states. Indeed, Greenland’s relatively small population is likely a key reason why Trump covets it and not, say, Cuba.

In conclusion, the history of U.S. northward expansionism offers insights into why the United States never annexed Canada, why Trump has framed his expansionist rhetoric in particular ways, and how costly that rhetoric is for U.S. foreign policy. While U.S. policymakers during the early to mid-1800s pursued sparsely populated western areas of what is now Canada, and strategists continued planning for northern campaigns in any potential U.S.-British war into the 1930s, at no point since the Constitution was ratified has annexing Canada as a whole been a central goal of U.S. foreign policy. Instead of belittling his diplomatic counterparts, Trump would serve U.S. national interests better by reemphasizing support for international territorial integrity — a norm that both benefits U.S. national security and distinguishes what the United States can offer as an international partner versus alternative visions for world order espoused by Russia or China.

Richard W. Maass is associate professor of political science at Old Dominion University, where he leads the U.S. foreign policy concentration within the graduate program in international studies. He is the author of The Picky Eagle: How Democracy and Xenophobia Limited U.S. Territorial Expansion (Cornell University Press, 2020) and his research has been published in journals including Texas National Security Review, International Security, International Studies Quarterly, and Diplomatic History.

Image: The Death of General Montgomery in the Attack on Quebec December 31 1775 by John Trumbull, accessed via Wikimedia Commons.