Remembering a Forgotten War

During a visit to the National Mall in Washington, D.C., you might see monuments and memorials dedicated to wars fought by the U.S.—from the Revolutionary War to World War I and the Vietnam War. But there’s one war that completely reshaped the American map and isn’t memorialized in our nation’s capital: the Mexican-American War.

That war, which ended 175 years ago, is perhaps the nation’s least remembered and least understood conflict—but it had huge ramifications. A defeated Mexico ceded half its land to the U.S., expanding the American nation all the way to the Pacific Ocean and shaping how the Southwest region looks today (see map).

During a visit to the National Mall in Washington, D.C., you might see monuments and memorials dedicated to wars fought by the U.S. They include the Revolutionary War, World War I, and the Vietnam War. But there’s one war that completely reshaped the American map and isn’t memorialized in our nation’s capital. It is the Mexican-American War.

That war, which ended 175 years ago, is perhaps the nation’s least remembered and least understood conflict. But it had huge implications. A defeated Mexico ceded half its land to the U.S. It expanded the American nation all the way to the Pacific Ocean and shaped how the Southwest region looks today (see map).

But the impact of the war went beyond geography. The controversial conflict pitted Americans against one another: those who favored westward expansion against those who admonished the U.S. for acting with brazen aggression against another nation. It further fueled the divide between slaveholding states and free states that would later explode into the Civil War (1861-65). And it left Mexico leery of its neighbor to the north.

That’s why experts say America’s “Forgotten War” deserves closer attention.

“A good portion of the western half of this country was acquired from Mexico through war,” says historian Amy S. Greenberg, author of a book on the conflict called A Wicked War. Learning that history, she adds, is key to understanding “the relationship between Mexico and the United States” today.

But the impact of the war went beyond geography. The controversial conflict pitted Americans against one another. Those who favored westward expansion were against those who admonished the U.S. for acting with brazen aggression against another nation. It further fueled the divide between slaveholding states and free states. The divide would later explode into the Civil War (1861-65). And it left Mexico leery of its neighbor to the north.

That’s why experts say America’s “Forgotten War” deserves closer attention.

“A good portion of the western half of this country was acquired from Mexico through war,” says historian Amy S. Greenberg. Greenberg is the author of a book on the conflict called A Wicked War. Learning that history, she adds, is key to understanding “the relationship between Mexico and the United States” today.

The seeds of the war were planted during the Texas Revolution of 1835-36. Settlers from the U.S. who’d migrated to the Mexican state of Coahuila y Tejas rebelled and declared themselves the Republic of Texas. The U.S. annexed that land in 1845, shortly after President James K. Polk took office (see timeline slideshow, below).

Polk was a staunch proponent of Manifest Destiny—the 19th-century
belief that the U.S. was destined to spread democracy across the continent. He wanted to lay claim to lands as far west as Mexican-controlled California. With the U.S. population booming at the time, the potential for fertile lands out West appealed to Polk and many others.

But many opposed westward expansion. Abolitionists and some lawmakers claimed the annexation of Texas was a land grab—an attempt by Polk, a slaveholding Southerner, and his fellow Democrats to add more slaveholding states to bolster their power in Congress.

Mexico viewed annexation as an act of war. Polk further antagonized Mexican officials by bringing U.S. troops into the Neuces Strip—an area of land between the Rio Grande and Neuces rivers that both the U.S. and Mexico claimed. On April 25, 1846, a skirmish broke out in the disputed area between U.S. scouts and the Mexican Army, leaving 11 Americans dead.

Polk’s opponents argued that he’d purposefully provoked Mexico. Nevertheless, he had his excuse for war, telling Congress that Mexico had “shed American blood on American soil.” On May 13, Congress approved Polk’s declaration of war.

The U.S. dominated on the battlefield despite frequently being outnumbered. U.S. soldiers were equipped with more modern weapons and led by more seasoned generals than their Mexican opponents. Early victories captivated the American public, which threw its support behind the war. For the first time, journalists embedded themselves with troops in battle, and people back home hungered for the latest news from the front.

The seeds of the war were planted during the Texas Revolution of 1835-36. Settlers from the U.S. who’d migrated to the Mexican state of Coahuila y Tejas rebelled. They declared themselves the Republic of Texas. The U.S. annexed that land in 1845, shortly after President James K. Polk took office (see timeline slideshow, below).

Polk was a staunch proponent of Manifest Destiny. That was the 19th-century belief that the U.S. was destined to spread democracy across the continent. He wanted to lay claim to lands as far west as Mexican-controlled California. With the U.S. population booming at the time, the potential for fertile lands out West appealed to Polk and many others.

But many opposed westward expansion. Abolitionists and some lawmakers claimed the annexation

of Texas was a land grab. They saw it as an attempt by Polk, a slaveholding Southerner, and his fellow Democrats to add more slaveholding states to bolster their power in Congress.

Mexico viewed annexation as an act of war. Polk further antagonized Mexican officials by bringing U.S. troops into the Neuces Strip. That was an area of land between the Rio Grande and Neuces rivers that both the U.S. and Mexico claimed. On April 25, 1846, a skirmish broke out in the disputed area between U.S. scouts and the Mexican Army. It left 11 Americans dead.

Polk’s opponents argued that he’d purposefully provoked Mexico. Nevertheless, he had his excuse for war, telling Congress that Mexico had “shed American blood on American soil.”

On May 13, Congress approved Polk’s declaration of war.

The U.S. dominated on the battlefield despite frequently being outnumbered. U.S. soldiers were equipped with more modern weapons. They were led by more seasoned generals than their Mexican opponents. Early victories captivated the American public, which threw its support behind the war. For the first time, journalists embedded themselves with troops in battle. People back home hungered for the latest news from the front.

But the conflict dragged on longer than Polk had expected, and a year in, public support for what critics dubbed “Polk’s War” waned. The death toll rose, and newspapers reported on U.S. soldiers committing atrocities against Mexican citizens. This led to the first national anti-war movement in the U.S.

One person who joined that movement was a little-known freshman congressman from Illinois: Abraham Lincoln. In December 1847, the future president demanded Polk show him the “particular spot of soil on which the blood of our citizens was so shed.”

Lincoln was calling into question Polk’s assertion that Mexico had started the war by firing shots on U.S. land. His statements echoed the public’s growing fatigue with the war and brought him his first taste of national recognition.

Increasing calls to end the war left Polk with little choice but to seek peace. Earlier that year, he’d sent Nicholas Trist, chief clerk of the U.S. State Department, to Mexico to begin negotiating a deal.

All the while, the war raged on. American troops stormed Mexico City, capturing the capital in September 1847 and backing Mexico into a corner. But negotiations still proved difficult. After many weeks of failed talks, Polk grew impatient with Trist, ordering him to return to Washington.

Trist defied the president. Working in secrecy, on February 2, 1848, he met with Mexican officials in the town of Guadalupe Hidalgo and signed a treaty to finally end the two-year-long war.

Polk was furious. But he sent the Treaty of Guadalupe Hidalgo to the Senate—which voted 38-14 in favor of it. Trist had stopped the bloodshed, but Polk immediately fired him upon his return.

The treaty forced Mexico to give up lands that now make up California, Nevada, Utah, New Mexico, most of Arizona, and parts of Colorado, Oklahoma, Kansas, Texas, and Wyoming. In exchange, the U.S. paid Mexico $15 million (equivalent to about $580 million today).

But money wasn’t the only cost. More than 12,500 American soldiers died—mainly from disease—along with at least 25,000 Mexicans, most of them civilians.

Ulysses S. Grant served in the war as a young West Point graduate and would later lead the Union Army in the Civil War­—and become the 18th president. He said in 1879: “I do not think there was ever a more wicked war than that waged by the United States on Mexico.”

The addition of so much U.S. land spurred debates over whether to extend slavery to the new territories, further dividing Northerners and Southerners. Those tensions would erupt 13 years later, with the outbreak of the Civil War.

But the conflict dragged on longer than Polk had expected. After a year, public support for what critics dubbed “Polk’s War” waned. The death toll rose. Newspapers reported on U.S. soldiers committing atrocities against Mexican citizens. This led to the first national anti-war movement in the U.S.

One person who joined that movement was a little-known freshman congressman from Illinois named Abraham Lincoln. In December 1847, the future president demanded Polk show him the “particular spot of soil on which the blood of our citizens was so shed.”

Lincoln was calling into question Polk’s assertion that Mexico had started the war by firing shots on U.S. land. His statements echoed the public’s growing fatigue with the war. It brought Lincoln his first taste of national recognition.

Increasing calls to end the war left Polk with little choice but to seek peace. Earlier that year, he’d sent Nicholas Trist, chief clerk of the U.S. State Department, to Mexico to begin negotiating a deal.

All the while, the war raged on. American troops stormed Mexico City, capturing the capital in September 1847. They backed Mexico into a corner. But negotiations still proved difficult. After many weeks of failed talks, Polk grew impatient with Trist, ordering him to return to Washington.

Trist defied the president. Working in secrecy, on February 2, 1848, he met with Mexican officials in the town of Guadalupe Hidalgo. They signed a treaty to finally end the two-year-long war.

Polk was furious. But he sent the Treaty of Guadalupe Hidalgo to the Senate. They voted 38-14 in favor of it. Trist had stopped the bloodshed, but Polk immediately fired him upon his return.

The treaty forced Mexico to give up lands that now make up California, Nevada, Utah, New Mexico, most of Arizona, and parts of Colorado, Oklahoma, Kansas, Texas, and Wyoming. In exchange, the U.S. paid Mexico $15 million (equivalent to about $580 million today).

But money wasn’t the only cost. More than 12,500 American soldiers died, mainly from disease. At least 25,000 Mexicans, most of them civilians, also died.

Ulysses S. Grant served in the war as a young West Point graduate. He would later lead the Union Army in the Civil War—and become the 18th president.

He said in 1879: “I do not think there was ever a more wicked war than that waged by the United States on Mexico.”

The addition of so much U.S. land spurred debates over whether to extend slavery to the new territories. This further divided Northerners and Southerners. Those tensions would erupt 13 years later, with the outbreak of the Civil War.

The Civil War wound up overshadowing the Mexican-American War. And today, 175 years after the war with Mexico, few people in the U.S. know much about it.

But it’s a different story across the border.

“The loss of territory is something that still haunts Mexican imagination,” says Erika Pani, a history professor at El Colegio de México in Mexico City. There, she says, the conflict is seen as “an unfair war” that left Mexico worried about ever “doing things that would provoke the U.S.”

However, relations between the two nations have come a long way. Today Mexico is America’s largest trading partner, and more than 37 million people of Mexican descent live in the U.S.—many on land once belonging to Mexico.

The Civil War wound up overshadowing the Mexican-American War. And today, 175 years after the war with Mexico, few people in the U.S. know much about it. But it’s a different story across the border.

“The loss of territory is something that still haunts Mexican imagination,” says Erika Pani, a history professor at El Colegio de México in Mexico City. There, she says, the conflict is seen as “an unfair war” that left Mexico worried about ever “doing things that would provoke the U.S.”

However, relations between the two nations have come a long way. Today Mexico is America’s largest trading partner. More than 37 million people of Mexican descent live in the U.S.—many on land that once belonged to Mexico.

But the 2,000-mile-long border continues to be a source of tension, with large numbers of undocumented immigrants from Central America, South America, and elsewhere crossing into the U.S. through Mexico. Relations between the two nations have also been strained by the rise of Mexican drug cartels and drug trafficking into the U.S.

To those who study U.S.-Mexico relations, though, one thing is certain: The futures of the two nations remain closely linked.

“Despite this being such a tense, complicated relationship, it is a relationship that is vibrant,” Pani says. “It’s built on mutual understanding of how far each of the countries can go.”

But the 2,000-mile-long border continues to be a source of tension. Large numbers of undocumented immigrants from Central America, South America, and elsewhere cross into the U.S. through Mexico. Relations between the two nations have also been strained by the rise of Mexican drug cartels and drug trafficking into the U.S.

To those who study U.S.-Mexico relations, though, one thing is certain. The futures of the two nations remain closely linked.

“Despite this being such a tense, complicated relationship, it is a relationship that is vibrant,” Pani says. “It’s built on mutual understanding of how far each of the countries can go.”