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

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.

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.

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′.

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.

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.

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."

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.

Support for slavery helped drive Texas to revolt against Mexico

Mexico abolished slavery in 1829, but many Anglo-American settlers in Texas brought enslaved people and refused to comply. Their desire to preserve slavery was a major factor in Texas’s 1836 rebellion and independence from Mexico.

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 Lincoln-Douglas debates sharpened the national divide over slavery

In 1858, Abraham Lincoln and Senator Stephen Douglas debated while competing for an Illinois Senate seat. Their seven debates, reprinted nationwide, brought the question of slavery to the forefront—further polarizing the country and propelling Lincoln to national prominence.

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.

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.

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.

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.

The Constitution included compromises that still shape the US today

The creation of the Constitution necessitated numerous compromises to accommodate the diverse interests of the states. The significant compromises included resolutions on debates over representation in Congress and the status of enslaved individuals.

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.

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 received only 40% of the popular vote in the 1860 election, highlighting the deep divisions in the country on the eve of the Civil War.

Cinco de Mayo holiday celebrations originated with California's Mexican Americans during the Civil War

California Latinos first celebrated Cinco de Mayo in 1862 through patriotic assemblies called Juntas Patrióticas. Ardent Union supporters, these individuals saw the Puebla victory as a win for democracy against both French imperialism and the Confederate cause.

Lincoln's original reconstruction vision prioritized reconciliation

Proposed in 1863, Lincoln's Ten Percent Plan offered lenient readmission for Southern states once 10% of voters pledged loyalty and ended slavery. It was adopted in a few Union-occupied areas but was only partially implemented before his assassination in 1865.

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.

Bills passed during the Civil War shaped postwar America

Despite the war with the South, Congress passed transformative laws like the Homestead Act and the Morrill Land-Grant College Act, which encouraged westward settlement and expanded higher education.

Congress's Wade-Davis Bill demanded harsher terms for Southern reentry

Passed in 1864, the Wade-Davis Bill required 50% of white male voters to swear loyalty and guarantee emancipation before readmission. Lincoln pocket-vetoed it, rejecting Congress's stricter approach.

The Mexican-American War trained future Civil War generals

Many key military leaders of the Civil War—including Ulysses S. Grant, Robert E. Lee, and Thomas “Stonewall” Jackson—first saw combat in the Mexican-American War, gaining battlefield experience that shaped their later commands.

Was the Civil War really about states' rights?

The Civil War was fought over slavery, and Confederate leaders and supporters admitted as much in the build-up to the war and after. But later on, after the South's defeat, the lie of the Lost Cause was pushed—and it persists to this day. This four-minute video details the story of the Lost Cause, "state's rights", Confederate monuments, and the machinations behind them.

The 1783 peace treaty with Britain formally ended the Revolutionary War and nearly doubled the size of the United States.

The Compromise of 1790 broke a deadlock over debt and the national capital

In 1790, Alexander Hamilton, James Madison, and Thomas Jefferson reached an agreement that allowed Congress to assume the states' war debts and to approve a permanent national capital on the Potomac River.

Madison urged Jefferson to accept the Louisiana Purchase despite constitutional concerns

As secretary of state, James Madison helped negotiate the 1803 Louisiana Purchase and persuaded Thomas Jefferson to proceed, arguing that the strategic and economic stakes outweighed the unresolved constitutional questions.

The disputed 1876 Presidential election accelerated the end of Reconstruction

The 1876 election between Rutherford B. Hayes and Samuel J. Tilden ended in a deadlock over contested Southern votes. To resolve the crisis, Democrats accepted Hayes's presidency in exchange for the withdrawal of federal troops—formally ending Reconstruction.

The Monroe Doctrine helped lead to the American occupation of territory abroad

This podcast explores how the policy motivated a century of US military intervention throughout Latin America, the Caribbean, and the Pacific—covering the annexation of Hawaii, the Spanish-American War, and occupations of Cuba, Haiti, and Panama.

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.

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.

In the midst of the Civil War, Lincoln rapidly expanded presidential power

Abraham Lincoln suspended habeas corpus, expanded the army without congressional approval, and issued the Emancipation Proclamation—despite likely lacking authority to unilaterally alter national slave law. His actions set precedents for expanded presidential power in wartime.

The Dred Scott decision denied citizenship to people of African descent

In 1857, the Supreme Court ruled in Dred Scott v. Sandford that Black Americans could not be US citizens. The decision heightened an already brewing conflict and became a key factor in pushing the nation toward civil war.

Ranchos were large land grants in California to Spanish, Mexican leading families

They were typically given to leading families or retired soldiers as means of settling the land with loyal people. The hundreds of ranchos have since shaped land-use policy in the area, determining plots of major cities and ranches today.

The Great Compromise created Congress's two-chamber structure during the Constitutional Convention

The Great Compromise of 1787 established a bicameral Congress, balancing population-based representation in the House with equal representation for each state in the Senate—a system designed to reconcile the competing interests of large and small states.

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.

The Civil War permanently strengthened federal power

The Civil War expanded federal power through emancipation, national military mobilization, and postwar civil rights laws, permanently strengthening the national government and shifting the balance of authority away from the states.

View animated battle maps from every major skirmish of the American Civil War.

Explore the social and cultural history of the Mexican-American War

Historian Peter Guardino joins host Don Wildman to explore how the war shaped ordinary lives on both sides of the border. Drawing from The Dead March, the episode reveals how culture, class, and ideology shaped the conflict and its consequences.

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 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.

Hear how the world reacted to the American Civil War

European nations closely watched the Civil War for its economic and political consequences. Some European nations quietly engaged diplomatically with the Confederacy but withheld recognition. When the Union made slavery's abolition a central cause, European public opinion turned sharply against the South.

Congress descended into fistfights, duels, and violence before the Civil War

In the decades before the Civil War, members of the United States Congress carried weapons, assaulted colleagues, and, in one case, a congressman killed another in a duel. The violence was driven largely by sectional conflict over slavery and foreshadowed the nation's descent into war.

A 1787 convention clash led to the creation of Congress’s two chambers

This article recounts debates on September 4, 1787, when delegates at the Constitutional Convention clashed over the balance of power between large and small states, driving the compromise that created the House and Senate.

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

The Reconstruction Amendments aimed to rebuild the nation and secure freedom after slavery

Ratified between 1865 and 1870 after the conclusion of the war, the 13th, 14th, and 15th Amendments abolished slavery, guaranteed citizenship and equal protection, and extended voting rights to Black men—transforming the Constitution's definition of liberty and equality.

The Electoral College was shaped in part to balance North–South power

This article examines how the Electoral College emerged from political compromise, including efforts to placate slave-owning Southern states and concerns that Northern states would dominate a direct national presidential vote.

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.