Support for slavery helped drive Texas to revolt against Mexico

Learn how Mexico’s anti-slavery stance shaped the US–Texas conflict

Historian Alice Baumgartner explores how Mexico’s abolition of slavery clashed with Anglo settlers' ambitions in Texas. The episode reveals how enslaved people fled south to freedom, reshaping the politics that led to Texas independence and the Mexican-American War.

American annexation of Texas eventually sparked war with Mexico

After Texas won independence from Mexico in 1836, the US annexed it in 1845—despite Mexico’s refusal to recognize Texas as separate. That annexation, combined with a heated border dispute, triggered the Mexican-American War the following year.

Mexico admired Lincoln for opposing the war and supporting Mexican sovereignty

As a congressman, Abraham Lincoln condemned the Mexican-American War as unjust. Years later, as president, he backed Mexico’s fight against French occupation. His principled stance earned enduring respect and monuments across Mexico.

The Compromise of 1850 tried to settle disputes over land gained from Mexico

Territory acquired in the Mexican-American War reignited fierce debates over slavery’s expansion. The Compromise of 1850 aimed to ease tensions by admitting California as a free state and letting other territories decide the issue—but the compromise ultimately failed and helped pave the way to the Civil War.

US westward expansion—and the status of slavery in the new territories—was a major cause of the American Civil War

The addition of new western lands forced the nation to confront whether slavery would spread beyond the South. Each debate over the admission of a new state sharpened the divide between free and slaveholding regions.

Mexico’s political chaos weakened its defense against US invasion

Mexico’s post-independence instability—marked by coups, power struggles, and weak central control—left its northern frontier vulnerable. That political fragmentation shaped Mexico’s unpreparedness during the Mexican-American War and helped enable US conquest.

How the US took half of Mexico

In just two years, the United States redrew the map of North America. Sparked by border disputes in Texas and fueled by President James Polk’s drive for expansion, the Mexican–American War (1846–1848) reshaped both nations.

According to Confederate leaders, the defense of slavery was the primary reason for secession.

Manifest destiny fueled US aggression against Mexico

The belief that the United States had a divine right to expand westward—known as manifest destiny—justified President Polk’s push for territorial conquest. It shaped public support for the Mexican-American War and framed the invasion as national destiny.

A Mexican village celebrates Juneteenth, honoring its past as a refuge for thousands of Black people who'd escaped slavery in Texas.

The Treaty of Guadalupe Hidalgo forced Mexico to surrender over half its territory

Signed in 1848, the Treaty of Guadalupe Hidalgo ended the war but came at a steep cost for Mexico—ceding 55% of its territory, including California and the Southwest, in exchange for $15 million and vague promises to protect Mexican residents.

The Royal Governor of Virginia offered slaves their freedom if they escaped and fought for the British in the American Revolutionary War.

The origins and growth of the Juneteenth holiday

The American holiday of Juneteenth celebrates the emancipation of African American slaves, a process which unfolded over the four years of the Civil War and several months afterward. June 19 took on special significance as the day Union officials proclaimed slaves free in Texas in 1865, the last holdout after the Civil War ended. Roughly 4 million people were freed from slavery as a result of emancipation. Read this brief article summarizing the holiday's development.

A wave of Latin American independence movements most likely prompted the Monroe Doctrine

Between 1810 and 1822, many Latin American colonies separated from Spanish rule, 10 in the last two years. Concerns that Spain and its European allies might try to regain these republics were a main reason behind Monroe's declaration.

The news delivered on the original Juneteenth freed enslaved people in Texas, but it also offered vague guidance on what they should do next.

US troops committed widespread atrocities during the Mexican-American War

American volunteer regiments frequently looted towns, raped civilians, and executed prisoners—especially in occupied northern Mexico. Historians have documented how racial hatred and impunity fueled war crimes that were rarely punished by military leadership.

Juneteenth celebrates the day that the last enslaved people were notified of the Emancipation Proclamation, 2 years after it was signed.

Irish immigrants deserted the US Army to fight for Mexico

During the Mexican-American War, hundreds of Irish Catholic immigrants—facing discrimination in the US Army—defected to Mexico and formed the Saint Patrick’s Battalion. Though many were captured and executed, they remain honored as heroes in Mexico.

Abolitionists shaped American history from the Revolution to the Civil War

Abolitionists of all backgrounds organized against slavery from the founding era onward. Historian Manisha Sinha argues that their decades of activism fundamentally shaped American democracy and made emancipation possible.

Despite the Juneteenth announcement that they were free, some enslaved people were still held captive.

A section condemning slavery, originally written by Thomas Jefferson, was cut from the Declaration of Independence.

The southbound Underground Railroad: finding freedom in Mexico

Until recently, the southbound Underground Railroad, as some scholars call it, has been largely overlooked, mainly because it left so few traces in surviving records. Read this article to learn more about this dangerous path and its travelers.

Thoreau's 'Civil Disobedience' was largely a protest against the Mexican-American War

Henry David Thoreau refused to pay taxes that funded what he saw as an unjust war waged to expand slavery. His act of protest inspired his famous essay "Civil Disobedience," a foundational text for nonviolent resistance.

Some historians claim that Mexico's victory at Puebla may have prevented France from arming the Confederacy

According to some experts, Napoleon III planned to ship weapons from Mexico to Confederate forces to break the Union naval blockade. The delay caused by the Battle of Puebla meant French resources didn't reach the Texas border until after the Union Army's decisive victory at Vicksburg.

France, Spain, and Britain formed a joint military alliance to force Mexico to repay its debts

In October 1861, the three powers signed the Convention of London and landed troops at Veracruz that December. Britain and Spain reached settlements with Mexico and withdrew. France refused and aimed to change the regime in power in Mexico.

Adams was a vocal opponent of slavery during the Revolutionary era

In letters written during the Revolution, Adams clearly opposed slavery—calling it an unjust scheme and highlighting the contradiction of fighting for freedom while enslaving others. Read it in her own words here in a letter to John Adams.

President Polk deliberately provoked war with Mexico

After Mexico refused to sell California and New Mexico, President James K. Polk ordered US troops into disputed territory between the Nueces River and the Rio Grande—knowing it would likely spark a conflict. When fighting broke out, he used it to justify declaring war.

Slavery in the US: a timeline

In 1619, a ship with 20 captives landed at Point Comfort in Virginia, ushering in the era of American slavery. Scroll through this timeline to learn more about slavery in the US and its long lasting effects.

Opposition to British taxes, regulation of trade was key to American independence

The economic situation in the colonies formed the backbone of the central events of the Revolution. British war debts caused it to lay the first direct taxes on colonists, cease their westward expansion claims, and adhere to stringent trade regulations, leading to backlash and eventual separation.

Mississippi didn't officially ratify the Thirteenth Amendment banning slavery until 2013, nearly 150 years after it passed.

The causes of American rebellion were multifaceted

British taxes on colonists to pay for the French and Indian War were just one element. Thousands of miles of separation between London and the Colonies, expanding territories, a distinct Colonial identity, and political conflicts combined to prompt the Revolution.

Formerly enslaved people in Houston purchased a plot of land in Houston in 1872 so they could have a place to celebrate Juneteenth.

Future President Abraham Lincoln challenged Polk’s justification for war with Mexico

As a freshman congressman, Abraham Lincoln introduced the “Spot Resolutions,” demanding President Polk prove that Mexico had attacked on US soil. This constituted Lincoln’s first major political stand and highlighted growing dissent over the war.

The Missouri Compromise temporarily eased tensions over slavery's expansion

Passed in 1820, the Missouri Compromise admitted Missouri as a slave state and Maine as a free state—maintaining the fragile balance between proslavery and antislavery states in Congress. It also banned slavery north of latitude 36°30′.

Discover why Texas runs its own electric grid, separate from the other US interconnections

In 1935, electrical utilities in the Lone Star State opted to rely on the state's own fossil fuel reserves to power an independent electric grid. While this prevented the federal oversight required for the Eastern and Western Interconnections that span multiple states, it also meant Texas's grid was unable to draw sufficient backup power during the winter 2021 power grid failure.

The US won every major battle of the Mexican-American War

Despite being outnumbered in key engagements, US forces defeated Mexican armies across every major front. Superior training, leadership, and logistics allowed the US to win decisively—capturing Mexico City without losing a single major battle.

Abraham Lincoln's victory in 1860 sparked Southern secession—even before his inauguration

Abraham Lincoln's election on an antislavery expansion platform convinced many Southerners that their way of life was under threat. Within three months, seven states seceded from the Union—forming the Confederacy—before Lincoln took office in March 1861.

A section condemning slavery was cut from the Declaration

Thomas Jefferson included a passage in his original draft denouncing slavery. This explainer from the Henry Ford Museum explores why Congress removed it to preserve colonial unity and how that decision shaped the nation's earliest political compromises.

The abolitionist movement long predated the Civil War

Beginning in the late 18th century, abolitionists like Frederick Douglass, William Lloyd Garrison, and Sojourner Truth campaigned through newspapers, lectures, and political action to end slavery.

Zachary Taylor became a national hero during the Mexican-American War

General Zachary Taylor led US forces to key victories in northern Mexico, earning widespread fame for his leadership. His popularity from the war propelled him to the presidency in 1848.

The US Army inherited the Apache Wars after the Mexican-American War

The resolution of the Mexican-American War inserted the US Army into an ongoing conflict between Apache groups and outside powers—transforming local resistance into a decades-long struggle against American expansion known as the Apache Wars.

Hamilton opposed slavery in principle but participated in the institution

Alexander Hamilton spoke against slavery, helped found the New York Manumission Society, and supported gradual emancipation while also participating in transactions involving enslaved people through his in-laws—and possibly within his own household, though historians debate this.

See the path Spanish conquistadors took to conquer the Aztecs

Spanish expeditions reached central Mexico as the Aztec Empire was expanding its influence. After securing bases in the Caribbean, they advanced west into Aztec territory, triggering a cascading conflict depicted in this interactive map and timeline.

Shays' rebellion pitted rebel veterans against the Revolution's leaders

The Revolutionary War led to independence and significant debt for most states. In 1786, a group of veterans and farmers from western Massachusetts protested against the state government’s increased taxes. Led by Daniel Shays, the group attempted to capture an armory in Springfield but failed.

France invaded Mexico to install a puppet monarchy and recover debt

Napoleon III used Mexico's default on foreign loans as cover for a larger imperial ambition: overthrowing President Benito Juárez's government and installing a French-backed monarchy. The Mexican army's surprise victory at Puebla helped delay those plans by nearly a year.

The Declaration of Independence was not only a statement of principles but also an appeal for military allies that the struggling colonists needed to survive.

The Kansas-Nebraska Act sparked violence that foreshadowed the Civil War

The 1854 Kansas-Nebraska Act let settlers vote on whether to allow slavery, repealing the Missouri Compromise. Competing proslavery and antislavery groups poured into Kansas, sparking years of bloody conflict known as "Bleeding Kansas."

Texas' includes German, Mexican, and Polish influences

Beef brisket, served with white bread and pickles, and sausage—a holdover from German immigration in the 1800s—are two of the most popular dishes. The southern end of the state brings together Mexican barbacoa and fajitas.

As Juneteenth celebrations spread throughout the country, they sometimes went by different names and took place on different days.

The Emancipation Proclamation shifted the purpose of the war for the Union

Issued on Jan. 1, 1863, the Emancipation Proclamation declared enslaved people in Confederate-held territory free, redefining the Union's cause from merely preserving the nation to abolishing slavery.