This blog was originally posted on May 12, 2021. We rerun it today on the 179th anniversary<\/em>.<\/p>\n During the first half of the nineteenth century, the young American republic expanded across the continent at a rapid pace. Purchasing the vast Louisiana territory from France, acquiring Florida from Spain, displacing Native sovereignties in the Southeast, annexing the republic of Texas, and eyeing the far reaches of the Pacific, expansionist-minded Americans considered it their \u201cmanifest destiny\u201d to \u201ccivilize\u201d North America with democracy, Christianity, and capitalism. Ralph Waldo Emerson voiced<\/a> this nearly unconquerable attitude when he described the United States in 1844 as \u201ca country of beginnings, of projects, of vast designs and expectations. It has no past: all has an onward and prospective look.\u201d<\/p>\n Manifest Destiny, however, also brought great instability to the federal Union. The acquisition of Texas in 1845 sparked a diplomatic crisis between the United States and Mexico. Both nations contested the location of Texas\u2019s southern border. Americans asserted a border along the Rio Grande, while the Mexicans placed the boundary north of that, along the Nueces River. To defend American claims, President James K. Polk deployed the military to the Nueces and ultimately directed General Zachary Taylor to advance south of the river. In response, on April 25, 1846, Mexican troops traversed the Rio Grande, engaged United States forces, and killed several American soldiers in the disputed territory. President James K. Polk demanded<\/a> that Congress declare war against Mexico to avenge the \u201cshed[ding] of American blood on American soil.\u201d On May 13, 1846, Congress gave Polk what he had always desired: a justification to invade Mexico, secure the Rio Grande as the United States\u2019s southern border, and seize the Mexican province of California. Sensing that Polk intentionally\u2014and immorally\u2014initiated the conflict, an obscure Whig congressman from Illinois named Abraham Lincoln garnered attention when he challenged the president\u2019s presumption<\/a> that American blood had indeed been spilled on American<\/em>, and not Mexican<\/em>, soil. Steadfast in his criticism of \u201cPolk\u2019s War,\u201d Lincoln lost his reelection bid in 1848, concluding his only term in Congress.\u00a0<\/p>\n The newspaper editor and poet Walt Whitman captured<\/a> the war fever that gripped an American public eager to \u201cchasten\u201d Mexico. \u201cLet our arms now be carried with a spirit which shall teach the world that, while we are not forward for a quarrel, America knows how to crush, as well as how to expand!\u201d Nearly 90,000 United States soldiers served during the war, two-thirds of whom were amateur citizen-soldiers. The New York Herald <\/em>depicted Americans\u2019 romantic view of volunteer military service in the republican tradition: \u201cOne of the highest tests of a good citizen, is the readiness or reluctance with which he yields his personal liberty . . . when at his country\u2019s call, he leaves his private pursuit and enters the field to fulfill the highest obligation a citizen owes his country.\u201d<\/p>\n A chauvinistic racism underwrote Americans\u2019 confidence in their Manifest Destiny. One ardent supporter of the war called Mexicans \u201creptiles in the path of progressive democracy\u201d<\/a> who could never advance beyond their allegedly primitive Indian and Spanish heritages. Only the strong arm of American military power, so went the argument, could wean Mexico away from what was seen as Catholic religious idolatry and veneration of dictators, replacing these with a stable republicanism. Mississippi volunteer William P. Rogers believed<\/a> that the United States carried a heavy burden to \u201cgreatly improve the condition of the poor Mexico.\u201d For Rogers<\/a>, the war was a paternalistic crusade \u201cpromotive of humanity and the cause of freedom and religion.\u201d<\/p>\n The war nevertheless garnered significant opposition. As a Democrat, President Polk embodied the bellicose assumptions of Manifest Destiny. He sneered at other national sovereignties, considering the United States fully entitled to swift territorial acquisitions across North America. The Whig Party lambasted Polk for instigating what it deemed an unprovoked and reckless war against Mexico. Georgia congressman Alexander H. Stephens condemned<\/a> the war as \u201cdownward progress<\/em>. It is a progress of party\u2014of excitement\u2014of lust for power\u2014a spirit of war\u2014aggression\u2014violence and licentiousness. It is a progress which, if indulged in, would soon sweep over all law, all order, and the Constitution itself.\u201d Statesman Henry Clay likewise denounced<\/a> Polk\u2019s militarism as a dangerous harbinger of national destabilization: \u201cWar unhinges society, disturbs its peaceful and regular industry, and scatters poisonous seeds of disease and immorality.\u201d\u00a0<\/p>\n Like many Whigs, Clay assumed that Polk purposely instigated the war to conquer land through which slavery might expand. Though a slaveholder himself, Clay considered the aggressive expansion of slavery a danger to national equilibrium, destabilizing sectional balance, radicalizing political extremes, and, he believed, planting the seeds of race war. Abolitionists expressed an even more earnest opposition to what Frederick Douglass called Polk\u2019s \u201cslaveholding crusade.\u201d Douglass excoriated the Democrats<\/a> for parading as \u201cthe accustomed panderers to slaveholders: nothing is either too mean, too dirty, or infamous for them, when commanded by the merciless man stealers of our country.\u201d<\/p>\n Nervous that \u201cPolk\u2019s War\u201d would yield abundant territorial bounties for slaveholders, Democratic Congressman David Wilmot<\/a> of Pennsylvania proposed in 1846 that, \u201cas an express and fundamental condition to the acquisition of any territory from the Republic of Mexico by the United States, by virtue of any treaty which may be negotiated between them . . . neither slavery nor involuntary servitude shall ever exist in any part of said territory.\u201d Wilmot aimed<\/a> to keep western lands free for white antislavery settlement but also free from African American residents.\u00a0<\/p>\n Although Wilmot\u2019s Proviso failed to pass Congress, its implications held great resonance for the future. When Mexico surrendered in 1848, the United States acquired as a prize of war the vast Mexican Cession, stretching from current-day New Mexico to California. The great twentieth-century American historian David M. Potter called<\/a> this moment \u201can ominous fulfillment\u201d of Manifest Destiny. Ralph Waldo Emerson predicted the trouble that would follow. He anticipated<\/a> that the United States would \u201cconquer Mexico, but it will be as the man who swallows the arsenic which will bring him down in turn. Mexico will poison us.\u201d By 1848, the triumph of national expansion had established the conditions of an irrepressible conflict over the question of slavery\u2019s expansion into the western territories.\u00a0<\/p>\n175 Years Ago Today: Congress Declares War on Mexico, Invoking Manifest Destiny and Destabilizing the House Divided<\/strong><\/h2>\n
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