The Forgotten War No Longer

By Michael Baumgartner

Saturday, October 04, 2025

 

When Americans walk the National Mall, they see monuments to the great struggles that shaped our nation. World War II, Korea, Vietnam — each has a fitting place in our capital’s national memory. Yet the war that made the United States a continental power, the U.S.–Mexican War of 1846–1848, is conspicuously absent. There is no national memorial in Washington to honor the 13,000 Americans who died and the more than 100,000 who served in that conflict, or the immense national transformation that flowed from their sacrifice.

 

This is a startling omission. The Mexican War was the third-most-important territorial war in American history, behind only the Revolution and the Civil War. It expanded U.S. territory by nearly 25 percent, including the territory that became the State of California. It resolved the Texas question, established a durable border with Mexico that was defined by treaty, and propelled America into the Pacific world with deep-water ports and new trade routes. Within months of peace, the 1848 Gold Rush began, drawing global migration to San Francisco and fueling the rise of America’s industrial might. Without the Mexican War, there would be no continental republic, no Pacific gateway, and no secure foundation for the United States’ emergence as a world power.

 

Even those who had opposed the war came to carry forward its legacy. Abraham Lincoln, as a young Whig congressman, criticized President James K. Polk’s conduct of the conflict. Yet as president, Lincoln relentlessly pressed the expansion made possible by the Treaty of Guadalupe Hidalgo — supporting the transcontinental railroad and telegraph, agricultural expansion, the land-grant university system, and homesteading policies that knitted together the nation’s new lands.

 

The war represents both a geopolitical hinge point and a continuity of American purpose: to complete the continental project and unleash the full power of a republic that spanned from shore to shore.

 

But the case for a memorial goes beyond territory and economics. The Mexican War also left profound institutional and moral legacies that shaped America’s character and deserve remembrance.

 

·        It was the Army’s proving ground: Nearly every major commander of the Civil War learned the trade of war in Mexico. Grant and McClellan fought as junior officers, gaining the field experience that later preserved the Union.

 

·        It taught us hard lessons in insurgency and occupation: U.S. forces quickly achieved battlefield dominance but then faced a stubborn guerrilla resistance. It was here that General Winfield Scott issued his famed General Orders on martial law — prohibiting pillage, protecting civilians, and establishing military commissions. These orders balanced firmness with restraint and became a direct forerunner of the Lieber Code and the international Geneva Conventions. They showed that America could temper victory with law, a principle that endures in our armed forces today.

 

·        We learned the value of diplomatic doggedness: While Polk sought quick leverage for land concessions, politics in Mexico made early negotiations impossible. It fell to Nicholas Trist, the State Department’s envoy, to ignore a presidential recall and press on with talks. His defiance, explained in a 65-page memorandum, helped produce the Treaty of Guadalupe Hidalgo — a framework that secured peace, normalized relations, and established the U.S.–Mexico border we still observe, with only minor changes later after the Gadsden Purchase of 1854. Trist’s stubborn professionalism reminds us that diplomacy requires courage as well as patience.

 

In all these ways, the Mexican War left marks far deeper than most Americans realize. It is not simply a “war of expansion,” as critics called it, but a crucible in which the Army was professionalized, the law of war advanced, and American diplomacy proved resilient. We would not be the America we know today but for the Mexican War.

 

That is why, as we approach the nation’s 250th anniversary, Congress should act to close this gap in our national memory. A fitting vehicle is before us: H.R.5510, the United States–Mexican War Memorial Act of 2025 that would designate Arlington Memorial Bridge as the U.S.–Mexican War Memorial Bridge. Built in the 1930s as a symbol of North–South reunion after the Civil War, the bridge stretches across the Potomac as a literal and figurative link in our civic landscape. To co-designate it for the Mexican War would extend that metaphor: from east to west, from shore to shore, honoring the sacrifice that completed America’s continental destiny. It would connect hallowed ground — Arlington, the nation’s resting place for its fallen — to the National Mall of remembrance, affirming that those who died in Mexico stand alongside the honored dead of every other American war.

 

Every war that shaped the United States should be honored in our capital. The Mexican War gave us California, secured the Southwest, opened the Pacific, and forged the officers and institutions that preserved the Union. The war’s 13,000 American dead fought and died as bravely as those in any conflict, and their legacy is with us still. On the Semiquincentennial of our Republic, it is time to ensure that this “forgotten war” is forgotten no longer.