Mexican Independence and a Multiracial Republic (1810–1821): Mexico’s wars of independence (1810–1821) were fought by a coalition of mestizo, Indigenous, and Afro-Mexican insurgents against Spanish rule. Leaders of the rebellion, including Priests Miguel Hidalgo and José María Morelos explicitly condemned slavery and called for racial equality as they rallied forces against the colonials. After a decade of struggle, the rebel conservative leader Agustín de Iturbide joined with Afro-Indigenous general Vicente Guerrero to proclaim the Plan of Iguala (1821), which declared that all citizens – “without distinction other than merit and virtue” – were equal under the law. Mexico won independence in 1821 with this multiracial vision in mind. In the new republic, Vicente Guerrero (of mixed African–Indigenous descent) became president and formally abolished slavery nationwide on September 16, 1829. These measures – abolition of slavery and a constitution granting equal rights to all races – created a political order radically different from that of the U.S. South.

To white American slaveholders, a neighboring country founded on these principles was deeply threatening to their racist ideology. Mexico’s example of a free, multiracial republic contradicted white supremacist claims of Black inferiority and offered enslaved African Americans a nearby sanctuary, undermining the social order of the slave states.

Mexican Policies Before the War: Mexico invited Anglo-American settlers to strengthen the population, economy, and defense of its sparsely inhabited northern frontier against Indigenous resistance, European invasion and potential U.S. expansion. The Mexican government granted land to those who pledged loyalty to Mexico, converted to Catholicism, and promised not to bring enslaved people. But many settlers, especially from the U.S. South, ignored these conditions and established slave plantations anyway.

To strengthen control, Mexico passed laws in the 1820s limiting further U.S. immigration and in 1829 abolished slavery nationwide under President Vicente Guerrero. Mexico also stationed garrisons, imposed customs duties, and attempted to centralize political power. These policies, meant to defend sovereignty and limit U.S. encroachment, convinced slaveholding settlers to rebel and call for U.S. annexation.

Texas Revolution and the Road to War: Texan insurgents declared independence in 1836. Santa Anna personally marched north to crush the rebellion. His army overwhelmed the volunteer garrison at the Alamo in March 1836, killing nearly all of its defenders. Angered Texans then rallied under General Sam Houston. On April 21, 1836, Houston staged a surprise attack at San Jacinto, routing Santa Anna’s forces and capturing the Mexican president.

Under duress Santa Anna signed the Treaties of Velasco, granting Texas independence. Texas remained a sovereign republic only until 1845, when the U.S. annexed it as a slave state – an act that directly provoked the Mexican–American War in 1846.

Mexican–American War (1846–1848): Myth vs. Reality of the Causes: American leaders justified the war in terms of Manifest Destiny and territorial expansion (“reannexation of Texas,” “open up Oregon,” etc.). Abolitionist Frederick Douglass refutted these claims when he attacked the war as a “slaveholders’ war” driven by Southern pro-slavery interests. As he wrote in 1848, the U.S. government was headed by “slavery, treachery and mad ambition.” He also noted the stark hypocrisy of war rhetoric: the nation had “elected James K. Polk, the slaveholder, as the friend of freedom” and then embarked on a war whose “lies” and “murderous plans” benefited slaveholders. Such critics saw that the war’s real goal was to seize new lands for slavery (south of the Missouri Compromise line), not to spread liberty. In the field, U.S. armies invaded northern Mexico, captured Monterrey and Mexico City, and inflicted heavy casualties.

Mexican Resistance on the Ground: Ordinary Mexicans fought back fiercely against the U.S. invasion, even when outgunned. In many occupied towns, civilians harassed U.S. soldiers by cutting supply lines, ambushing patrols, and refusing to sell food. Women in places like Monterrey and Mexico City sometimes attacked soldiers directly, hurling stones, boiling water, or oil from rooftops onto troops marching through the streets. Rancheros and peasants carried out guerrilla warfare across the countryside, targeting wagon trains and isolated detachments, forcing the U.S. Army to devote thousands of troops to guard supply routes. U.S. soldiers themselves described the constant danger: one noted that “every bush hides a guerrilla.” Though these acts rarely stopped the larger tide of the war, they made occupation costly and curbed the ambition of U.S. policymakers.

The Treaty of Guadalupe Hidalgo: By February 1848 the Treaty of Guadalupe Hidalgo ended the war. Mexico ceded over half its territory, including California and New Mexico, to the United States. In theory, the treaty guaranteed protection of property and civil rights for Mexicans in the ceded lands. In practice, however, many Tejano and Californio were marginalized, robbed, and degraded to second-class citizens.

Theft of Land: The most devastating outcome of U.S. conquest was the massive theft of land from both Native and Mexican communities. In California and the Southwest, Mexican landowners (Californios and Tejanos) were promised protection of their property under the Treaty of Guadalupe Hidalgo, yet U.S. courts and squatters quickly stripped them of their ranchos. Legal battles dragged on for years in English-only courts, with Anglo lawyers charging exorbitant fees and judges often ruling against Mexican claimants. Many families were forced to sell land at low prices just to pay court costs, and others lost everything to violent seizure by vigilantes and squatters.

Native Americans, already forced onto reservations, faced constant encroachment as settlers grazed cattle, mined, or farmed on their lands with impunity. The federal government further eroded Native landholding with allotment policies later in the century, but even in the 1850s–60s, outright theft was rampant. In both cases—whether through courts, legislation, or violence—the U.S. system turned promises of protection into tools of dispossession, ensuring that white settlers gained control of the most fertile and valuable lands in the West.

African American Resistance: Flight to Mexico: Even before and especially after the war, many enslaved people fled southward, using what historians call the “Underground Railroad to Mexico.” Mexico’s antislavery laws made it a refuge.

One famous case involved the Black Seminoles — a community of Black (and mixed-heritage) Seminole Indians originally in Florida and Indian Territory. In 1850-1851 the Black Seminole leader John Horse (sometimes called Wild Cat) guided over 300 Seminoles and Black allies into Mexican territory. The Mexican government granted them a large military colony in Coahuila (about 70,000 acres) to live and farm as free people in exchange for serving as border guards. Within a year their numbers grew to about 356 people (three-quarters of them runaway slaves) in the colony known today as El Nacimiento de los Negros. There they took on the name “Mascogos,” built homes, and defended northern Mexico from Apache and Comanche raids. The Mexican government’s protection of these fugitives starkly contrasted with U.S. slave catchers’ attempts to kidnap them.

California: State-Sanctioned Genocide: The Gold Rush (beginning 1848) and California statehood (1850) brought a rapid influx of white settlers, along with open hostility toward Native peoples. California’s first state government under the United States embraced a policy of extermination. Governor Peter Burnett declared in 1851 that the state was engaged in a “war of extermination” against California Indians (implying it would continue “until the Indian race becomes extinct”). California even passed an Act for the Government and Protection of Indians (1850) which, despite its benign name, legalized forced labor of Native Californians under the pretext of “apprenticeship” and theft of children. Under this law and local “vigilance” committees, settlers routinely rounded up Indigenous people for enslavement or execution. Militia units were raised at public expense to hunt tribes; bounties were placed on Native lives, and volunteer militia were funded by the government.

Most atrociously, 1856–1859 saw the Round Valley massacres and the Yuki genocide: over those three years hundreds of white settlers in Mendocino County murdered more than 1,000 Yuki and other local Indians. In 1859, the so-called “Eel River Rangers,” led by Walter S. Jarboe, wiped out large Native bands in the Eel and Round Valleys. Jarboe’s militia killed at least 283 Indians in six months and was later reimbursed by the state and federal governments for its “work”. Other massacres—such as the 1860 killing of 80–250 Wiyot people (mostly women and children) in Humboldt County—occurred with impunity. In short, California’s official policy was ethnic cleansing of Native inhabitants to seize their land. These state-sanctioned killing campaigns, often with federal support, drove California’s native population down by tens of thousands.

Between 1846 and 1870, California’s Native population collapsed from about 150,000 people to fewer than 30,000. This staggering decline was not simply the result of disease but the product of deliberate policies: militias funded by the state, forced removals, and legalized enslavement under the 1850 “Act for the Government and Protection of Indians.” Governor Peter Burnett’s declaration of a “war of extermination” proved tragically accurate — California’s admission to the Union was accompanied by one of the most devastating genocides in U.S. history.

Native Resistance Beyond California: Across the newly seized Southwest, Native nations resisted U.S. expansion with determination. The Comanche, long a dominant power on the southern plains, continued their raids into Texas and northern Mexico, forcing U.S. settlers to fortify towns and travel in armed groups. Apache bands fought a generations-long guerrilla war, striking ranches and army posts, retreating into the deserts and mountains where U.S. troops struggled to pursue them. In the 1860s, the Navajo resisted U.S. incursions until the military forced thousands on the “Long Walk” to the Bosque Redondo reservation in New Mexico, a march where hundreds died. Farther north, the Lakota and Cheyenne defended the plains against settlers and soldiers, culminating in victories like Red Cloud’s War in the 1860s.

The Reservation System: The reservation system took shape in the mid-19th century as a way to confine Native nations and clear space for white settlers. After the U.S. victory over Mexico, Native communities in California, the Southwest, and the Great Plains suddenly found themselves under the control of Washington. Treaties made in the 1850s promised food, tools, and schools in exchange for Native land cessions, but these promises were rarely kept. Reservations were often deliberately placed on poor, arid land far from traditional hunting or farming grounds. This forced tribes into dependency on government rations, which were frequently delayed or stolen by corrupt U.S. agents. Federal policy treated reservations as holding pens where Native peoples could be watched, controlled, and kept away from settler society.

Missionaries and officials insisted that Native children be educated in English, taught Christianity, and trained to farm in the Anglo style. Families were pressured—or coerced—to abandon ceremonies, languages, and communal ways of life. This set the stage for the later boarding school system, but the roots were already in the 1850s reservation regime. For Native nations, this meant not only the loss of land but also an assault on their cultural survival.

Resistance was constant: many left the assigned reservations, fought U.S. troops, or maintained ceremonies in secret.

Mexican Communities: Mexicans living in the annexed territories suddenly found themselves under U.S. rule. The Treaty of Guadalupe Hidalgo had promised to protect their property and civil rights, but in practice many were cheated out of land by incoming settlers or by courts that did not recognize Mexican land grants. Men who were offered U.S. citizenship often faced discrimination; Spanish-speaking communities were marginalized. (In California, for example, the Treaty rights of Californios were frequently violated.) Thus, Mexican citizens suffered dispossession after the war: tribes were confined to reservations, and Mexicans became a subordinate minority in their own land.

In the territory of New Mexico, which had been part of Mexico until 1848, local communities fiercely resisted U.S. occupation. When General Stephen Kearny’s army marched into Santa Fe in 1846, U.S. officials assumed Mexican and Pueblo residents would accept the new order. Instead, resentment boiled over in January 1847 in what became known as the Taos Revolt. A coalition of Mexican citizens and Taos Pueblo fighters rose up, killing the newly appointed U.S. governor, Charles Bent, and several other officials. Insurgents besieged American positions, drawing on community networks and Pueblo strongholds for support. Although U.S. troops quickly retaliated—storming the Taos Pueblo church and executing dozens of prisoners—the revolt showed that conquest was never smooth or universally accepted.

In the decades after the Taos Revolt, Mexican communities in New Mexico faced waves of hostility from Anglo settlers and vigilante groups.

Unlike in California or Texas, Mexican families in New Mexico retained much of their land, language, and political influence. Strong community networks, high population numbers, and strategic alliances allowed New Mexican elites to keep a measure of economic power and cultural presence well into the 20th century. This persistence meant that even as Manifest Destiny reshaped much of the West, New Mexico remained a place where Mexican identity and authority endured.

References (APA style):

Douglass, F. (1848, January 21). The War with Mexico. North Star. Retrieved from History Is a Weapon websitehistoryisaweapon.comlearningforjustice.org.

Grant, R. (2022, July/August). The southbound Underground Railroad brought thousands of enslaved Americans to Mexico. Smithsonian Magazine. Retrieved from [SmithsonianMag.com]smithsonianmag.comsmithsonianmag.com.

Smithsonian Magazine. (2022). The Southbound Underground Railroad Brought Thousands of Enslaved Americans to Mexico. (Article by R. Grant). Retrieved from [SmithsonianMag.com]smithsonianmag.comsmithsonianmag.com.

Treaty of Guadalupe Hidalgo (1848). U.S. National Archives. Retrieved from [archives.gov]archives.gov.

Valdovinos, S. (2019). California Genocide: A History of Anti-Indian Violence. University of Oklahoma Press (cited via Wikipedia).

Rawls, J. (2012). “Mexican/American Period: The Aftermath,” Autry Museum of the American West (online exhibition). Retrieved from [theautry.org]theautry.orgtheautry.org.

Tschaikovsky, D. (n.d.). The Texas Revolution. Texas State Historical Association. Retrieved from [tshaonline.org]en.wikipedia.orgen.wikipedia.org.

Williams, K., & White, R. (2000). An Indigenous Peoples’ History of the United States. Beacon Press (context on manifest destiny and expansion).

Woolfolk, J. L. (2017). Struggle and Survival on the Rio Grande: Anglo-Americans in Occupied Mexico. Texas A&M University Press (context on Texas and annexation).