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The Mexican-American War was a conflict between the United States and Mexico, fought from April 1846 to February 1848. Won by the Americans and damned by its contemporary critics as expansionist, it resulted in the U.S. gaining more than 500,000 square miles (1,300,000 square km) of Mexican territory extending westward from the Rio Grande to the Pacific Ocean. It stemmed from the annexation of the Republic of Texas by the U.S. in 1845 and from a dispute over whether Texas ended at the Nueces River (the Mexican claim) or the Rio Grande (the U.S. claim).
Under the Treaty of Guadalupe Hidalgo, which settled the Mexican-American War, the United States gained more than 500,000 square miles (1,300,000 square km) of land, expanding U.S. territory by about one-third. Mexico ceded nearly all the territory now included in the U.S. states of New Mexico, Utah, Nevada, Arizona, California, Texas, and western Colorado for $15 million and U.S. assumption of its citizens’ claims against Mexico.
Treaty of Guadalupe Hidalgo
Read more about the Treaty of Guadalupe Hidalgo.Mexican-American War, also called Mexican War, Spanish Guerra de 1847 or Guerra de Estados Unidos a Mexico (“War of the United States Against Mexico”), war between the United States and Mexico (April 1846–February 1848) stemming from the United States’ annexation of Texas in 1845 and from a dispute over whether Texas ended at the Nueces River (Mexican claim) or the Rio Grande (U.S. claim). The war—in which U.S. forces were consistently victorious—resulted in the United States’ acquisition of more than 500,000 square miles (1,300,000 square km) of Mexican territory extending westward from the Rio Grande to the Pacific Ocean.
Mexico severed relations with the United States in March 1845, shortly after the U.S. annexation of Texas. In September U.S. Pres. James K. Polk sent John Slidell on a secret mission to Mexico City to negotiate the disputed Texas border, settle U.S. claims against Mexico, and purchase New Mexico and California for up to $30 million. Mexican Pres. José Joaquín Herrera, aware in advance of Slidell’s intention of dismembering the country, refused to receive him. When Polk learned of the snub, he ordered troops under Gen. Zachary Taylor to occupy the disputed area between the Nueces and the Rio Grande (January 1846).
On May 9, 1846, Polk began to prepare a war message to Congress, justifying hostilities on the grounds of Mexican refusal to pay U.S. claims and refusal to negotiate with Slidell. That evening he received word that Mexican troops had crossed the Rio Grande on April 25 and attacked Taylor’s troops, killing or injuring 16 of them. In his quickly revised war message—delivered to Congress on May 11—Polk claimed that Mexico had “invaded our territory and shed American blood on American soil.”
Congress overwhelmingly approved a declaration of war on May 13, but the United States entered the war divided. Democrats, especially those in the Southwest, strongly favoured the conflict. Most Whigs viewed Polk’s motives as conscienceless land grabbing. Indeed, from the outset, Whigs in both the Senate and the House challenged the veracity of Polk’s assertion that the initial conflict between U.S. and Mexican forces had taken place in U.S. territory. Further, legislators were at odds over whether Polk had the right to unilaterally declare that a state of war existed. Principally at issue was where the encounter had actually taken place and the willingness of Americans to acknowledge the Mexican contention that the Nueces River formed the border between the two countries. Active Whig opposition not only to the legitimacy of Polk’s claim but also to the war itself continued well into the conflict. In December 1846 Polk accused his Whig doubters of treason. In January 1847 the by-then Whig-controlled House voted 85 to 81 to censure Polk for having “unnecessarily and unconstitutionally” initiated war with Mexico.
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Among the most-aggressive challenges to the legitimacy of Polk’s casus belli was that offered by future president Abraham Lincoln, then a first-term member of the House of Representatives from Illinois. In December 1847 Lincoln introduced eight “Spot Resolutions,” which placed the analysis of Polk’s claim in a carefully delineated historical context that sought to
obtain a full knowledge of all the facts which go to establish whether the particular spot of soil on which the blood of our citizens was so shed was, or was not, our own soil at that time.
Ultimately, the House did not act on Lincoln’s resolutions, and Polk remained steadfast in his claim that the conflict was a just war.
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Abolitionists saw the war as an attempt by the slave states to extend slavery and enhance their power with the creation of additional slave states out of the soon-to-be-acquired Mexican lands. One abolitionist who agreed with that interpretation was author Henry David Thoreau, who was incarcerated in July 1846 when he refused to pay six years’ worth of back poll taxes because he felt the U.S. government’s prosecution of the war with Mexico was immoral. Although he spent only a single night in jail (his aunt, against his wishes, paid the taxes, thus securing his release), Thoreau documented his opposition to the government’s actions in his famous book-length essay Civil Disobedience (1849), insisting that if an injustice of government is
of such a nature that it requires you to be the agent of injustice to another, then, I say, break the law. Let your life be a counter friction to stop the machine.
The Mexican War of Independence was in reality a series of revolts that grew out of the increasing political turmoil both in Spain and Mexico at the beginning of the nineteenth century. During the French revolutionary and Napoleonic wars Spain fought both as an ally and as an enemy of France and suffered frequent interruptions in its commerce with its American colonies. Burdened with mounting war debts and facing a deepening economic crisis, Spanish rulers settled on extracting increased colonial revenues to meet European obligations. A royal decree in 1804 ordered imperial officials to confiscate certain church assets and place them at the disposal of the crown. In Mexico, as the church called in loans and mortgages and credit from that source dried up, a financial crisis emerged that was aggravated by an economic downturn caused by disruptions in overseas trade and bad harvests. Growing disaffection in New Spain received considerable reinforcement when Napoleon invaded Spain in 1808 and forced Ferdinand VII to abdicate the Spanish throne in favor of his brother Joseph. Rejection of the French usurper was unanimous throughout the Spanish empire, even if unanimity of action did not follow. Mexico's criollo elite, long eager for a greater role in local government, seized the opportunity to promote a provisional government (junta gubernativa) acting in the name of the legitimate king, Ferdinand VII. Peninsular Spaniards, who made up the majority of the upper hierarchy of the church and held most other top colonial posts, favored rule by the existing viceroy and audiencia. Neither group was interested in seeing the Indian and mestizo masses, which were considered unstable, get involved in the crisis of government. The viceroy, Jose de Iturrigaray, miscalculated the strength and solidarity of the criollos and sided with them, only to be unseated in a palace coup by the well-organized peninsulars. Having dispatched Iturrigaray for Spain and arrested influential creoles, the peninsulars named Pedro Garibay, an aged Spanish field marshal, viceroy. While Mexico City entered an uneasy calm in 1809, other parts of the viceroyalty became increasingly agitated. Continued disruptions in manufacturing caused by changing overseas trade, along with poor crops in 1809, led to an economic slowdown and famine in 1810, particularly in the Bajío, the viceroyalty's leading mining center. It was in the area of Querétaro, an important agricultural center in the region, that a number of disgruntled criollos, hoping to wrest power from the peninsulars, determined to employ the Indian and mixed-blood peasantry in the effort. Among the conspirators was the parish priest of Dolores, a small agricultural town east of Guanajuato. It fell to Father Miguel Hidalgo y Costilla to begin the rebellion formally against bad government and Spaniards on the morning of September 16, 1810, from the steps of the parish church, after he received news that the conspiracy had been exposed. The early progress of the revolt, particularly the looting of Guanajuato, which was accompanied by the killing of large numbers of peninsulars and criollos, led these groups to close ranks behind the viceregal government. The able leadership of the new viceroy, Francisco Javier Venegas, and Gen. Félix María Calleja (who subsequently succeeded Venegas as viceroy) soon had Hidalgo's Indian army in retreat. In January 1811 Calleja defeated Hidalgo outside Guadalajara, forcing the rebel leadership to flee northward, toward the United States. Hidalgo and the insurgent leadership hoped to find at least temporary refuge in the northeastern provinces, where rebellion had also broken out. In Nuevo Santander Royalist forces mutinied against the governor when ordered to march toward San Luis Potosí to fight the insurgents. Governor Manuel Antonio Cordero y Bustamante of Coahuila suffered the defection of his 700 troops in early January 1811, when confronted by a rebel army of between 7,000 and 8,000. Insurgents dispatched to take control of Nuevo León found local officials there more than willing to declare in favor of Hidalgo. In Texas, Governor Manuel Salcedo was unseated on January 22, 1811, by a rebellious former militia officer, Juan Bautista de las Casas, with support from the troops garrisoning San Antonio (see CASAS REVOLT). As in the central parts of the viceroyalty, insurgent successes in the north proved short-lived. Under orders from Viceroy Venegas, Gen. Joaquín de Arredondo successfully invaded Nuevo Santander in February 1811. At the beginning of March, loyalists under the leadership of Juan Manuel Zambrano wrested power from Casas, and in Coahuila loyalists managed to recapture Monclova in mid-March. On March 21, 1811, a loyalist officer, Ignacio Elizondo, ambushed the insurgent leadership, Ignacio Allende, Father Hidalgo, and their chief lieutenants, at the Wells of Baján on the road to Monclova. With this action the northeastern provinces returned to Royalist control. Only in Texas, which in the summer of 1812 suffered an invasion from the United States under the leadership of José Bernardo Gutiérrez de Lara and Augustus Magee, was royal authority seriously threatened. In August of 1813, however, General Arredondo defeated the rebels at the battle of Medina and secured Texas for the Spanish crown. After the capture and execution of Hidalgo and Allende, José María Morelos y Pavón assumed leadership of the independence struggle. Morelos, like Hidalgo a cleric, had a clearer vision of Mexico's future and employed superior organizational and political skills. Under Morelos a clear declaration of independence from Spain was made and a constitution drafted. Still, Morelos was unable to obtain criollo backing for the struggle and he had to rely on mestizo support. He lost his position of leadership to his rivals in the movement, however, and in November 1815, while defending the escape of the insurgent government from loyalist attack, he was captured and executed. Subsequently the struggle for independence broke down into a series of local revolts and guerrilla actions that did not seriously threaten royal authority in Mexico until 1820. The final push for independence resulted from Mexican reaction to revolutionary events in Spain that undermined the last vestiges of Spanish authority in the colonies. In January 1820 an army that assembled in Cádiz for an attempt to reconquer Argentina mutinied and sparked rebellion among other army units throughout Spain. Joined in revolt by liberals, radicals, and anyone opposed to Ferdinand's absolutist rule of the previous six years, the rebellious military forced the king to restore the Constitution of 1812. Once seated, the constitutional Cortes proved unwilling to address American grievances or to extend equal standing to colonials within the new order. Political tensions between reform-minded Mexicans and colonial authorities led Agustín de Iturbide, a royal officer with a record of success against earlier rebels, to come to terms with the leading Mexican insurgent at the time, Vicente R. Guerrero. Together, on February 24, 1821, they proposed a blueprint for independence called the Plan de Iguala. The plan offered three guarantees— preservation of the Catholic Church's status, the independence of Mexico as a constitutional monarchy, and equality of Spaniards and criollos. Although viceregal authorities tried to resist, the plan met with widespread approval both in civilian and military quarters. By the end of July 1821, when Juan O'Donoju arrived to take over the reins of colonial government, the loyalists controlled only Mexico City and Veracruz. Recognizing that all was lost, O'Donoju met with Iturbide at the town of Córdoba, where on August 24, 1821, he signed a treaty granting Mexico independence.
Vito Alessio Robles, Coahuila y Texas en la época colonial (Mexico City: Editorial Cultura, 1938; 2d ed., Mexico City: Editorial Porrúa, 1978). Timothy Anna, "The Independence of Mexico and Central America," in The Independence of Latin America, ed. Leslie Bethell (Cambridge University Press, 1987). Donald E. Chipman, Spanish Texas, 1519–1821 (Austin: University of Texas Press, 1992). Julia Kathryn Garrett, Green Flag Over Texas: A Story of the Last Years of Spain in Texas (Austin: Pemberton Press, 1939). Michael C. Meyer and William L. Sherman, The Course of Mexican History (New York: Oxford University Press, 1979). John Tutino, From Insurrection to Revolution: Social Bases of Agrarian Violence, 1750–1940 (Princeton: Princeton University Press, 1986).
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The following, adapted from the Chicago Manual of Style, 15th edition, is the preferred citation for this entry.
Jesús "Frank" de la Teja, “Mexican War of Independence,” Handbook of Texas Online, accessed October 31, 2022, //www.tshaonline.org/handbook/entries/mexican-war-of-independence.
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