How the US took half of Mexico

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 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.

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.

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 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.

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.

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.

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.

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.

The Mexican-American War led to the birth of the Associated Press

To cover the distant war efficiently, rival New York newspapers pooled resources to share reports from the front—forming what became the Associated Press. The war marked a turning point in how Americans received real-time news about foreign conflicts.

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.

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.

The Louisiana Purchase nearly doubled America’s size in 1803

Acquired from France for $15M, the Louisiana Purchase added 828,000 square miles to the United States—stretching from the Mississippi River to the Rockies. US ambassadors in France signed the papers to buy the tract from the embattled Napoleon Bonaparte for a mere $15M before Jefferson learned the terms, due to the advantageous nature of the deal.

How the US entered WWI in 1917

Originally taking a position of neutrality during the course of World War I, the United States of America eventually relented. Entering the war in 1917, support for the British and French had risen and Americans were incensed by Germany's overtures to Mexico and U-boat attacks that sank ships and ended American lives. See how and why the US entered WWI in this article.

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.

European colonization dramatically reshaped Native American life

As European settlers expanded across North America, Native Americans faced displacement, violence, and forced negotiations. Colonial powers used trade relationships, treaties, and military force to reshape Indigenous communities and claim their territories.

The US handed control of the canal back to Panama in 1999

This was the result of two treaties signed during President Jimmy Carter's presidency, one shifting control to Panama and the other declaring the canal zone neutral. In recent years, US officials have suggested the US may retake control. Experts agree that the only viable way would be through military force.

The Civil War turned the Continental Divide into an American symbol of identity

Historians argue that the boundary only became a celebrated American symbol in the 1860s, when Civil War-era leaders promoted a west-east geographic divide to replace the devastating north-south political divide, and that the term's use spiked after the transcontinental railroad crossed it in 1868.

A timeline of US immigration laws

The United States began regulating immigration soon after it won independence from Great Britain, and the laws since enacted have reflected the politics and migrant flows of the times. Here's a timeline of key immigration laws from 1790 to 2014, according to the Pew Research Center.

The diplomat who implemented Monroe's policy introduced the poinsettia to the United States

Joel Roberts Poinsett, appointed as the first US minister to Mexico in 1825 following the doctrine's announcement, took cuttings of a vibrant Mexican plant called the cuetlaxochitl during his time there. Americans loved the foliage and named it after him.

The Sykes-Picot agreement as seen through Arab eyes

After WWI, the borders of the Middle East were redrawn by two men: Mark Sykes (UK) and Francois Picot (France). Signed in 1916, their secret agreement divided one of the most volatile regions in the world into states, cutting through ethnic and...

Every US state's top import partner

Mexico, Canada, and China are the top trade partners for 42 of the states.

Mid-decade redistricting is historically rare in modern US history

States have generally redrawn districts only once per decade following the census, with mid-decade redistricting occurring infrequently and usually prompted by court orders or unusual political circumstances.

Madison and Jefferson forged a political alliance that shaped the early US republic

Beginning in the 1780s, James Madison and Thomas Jefferson collaborated closely to oppose centralized power, to found the Democratic-Republican Party, and to guide the nation's early debates on constitutional and foreign policy.

Explore an interactive map of battles from the American Revolution, along with detailed summaries of each engagement

The United States is one of only around two dozen countries with a fully federal system of government, in which power is divided between national and state governments.

The United States has had a tumultuous relationship with Cuba since its 1959 revolution, highlighted by a nuclear crisis and a decades-long trade embargo.

See a 3D reconstruction of Tenochtitlan, the Aztec capital that was home to an estimated population of 200,000 to 400,000.

'Grand Canyon of the Yellowstone,' a work by American painter Thomas Moran, inspired Congress to establish Yellowstone National Park.

Hear about the 250-year history of the United States Postal Service, complete with some of its strangest deliveries, important innovations, and the figures that made it an American institution.

Abraham Lincoln was almost assassinated weeks before his inauguration as he traveled from Illinois to DC through Baltimore in 1861; it took two independent claims for Lincoln to be convinced the threat was real

Gerrymandering works through two techniques: cracking opposing voters across districts to dilute their power, and packing them into a few to waste their votes in lopsided majorities.

Trace how the Bill of Rights, inspired by centuries of political theory, took shape between 1774 and 1789.

Long before Major League Baseball began allowing instant replay for balls and strikes, an umpire reluctantly used the technology to determine whether a hit was a home run, a move that inadvertently ushered in a new era for the sport.

The Great Salt Lake's distinct dual coloration results from high-salinity organisms that only live in the northern portion and produce a purple protein.

The US first hosted the World Cup in 1994, a tournament that lives in soccer infamy for its poor planning and the murder of Colombian player Andres Escobar, who'd accidentally scored on his own net.

The Russia-Ukraine conflict is the largest ground war in Europe since World War II in casualties, forces mobilized, and displacement of civilians.

'Shogun,' a 1980s TV series, helped popularize sushi in the US by stimulating an American interest in Japanese culture.

While El Niño moves warm Pacific Ocean waters east along the equator, La Niña moves them west, shifting where rainfall will become more common for months.

See how fireworks are made and learn how metals like magnesium and copper are responsible for different colors.

The concept of phantom limbs, the perception that amputated limbs are still present, dates back to a French military surgeon in the 16th century.

While the first exchange-traded fund (a 'basket' of different assets that can be bought and sold on a stock exchange) in the US only launched in 1993, the global ETF market has grown to more than $10T in the short time since.

In 1945, Surrealist artist Salvador Dalí and legendary animator Walt Disney began collaborating on a short film that was not completed until 2003, years after both men had died.

The American cockroach is actually from Africa, an apparent hitchhiker aboard ships carrying enslaved people, with evidence suggesting the bug may have arrived in the New World as early as the 1600s.

View the ten deadliest tornadoes in US history.

The Beatles' US label rejected the band's first two singles, 'Please Please Me' and 'From Me to You,' with one executive calling the band 'dead in the water.'

Some coin denominations have ridges etched on their sides, partly to prevent counterfeiting, in a practice called 'reeding.'

US housing costs have risen by roughly 175% between 1991 and 2026—but a growing number of Gen Zers are becoming homeowners anyway. In 2025, 4% of homebuyers were Gen Z, up from 3% the year before.