Manifest Destiny & Mexican-American War Introduction

To understand some of the long-term effects of this tussle with Mexico, we have to understand the background of the war and the debate over Texas. 

The year was 1836 and Texans were high-fiving each other and shouting "Remember the Alamo!" as they celebrated their independence from Mexico. Mexico was looking the other way with its fingers in its ears pretending the whole thing never happened. 

America, on the other hand, was debating the idea of annexing Texas to make it a part of the Union. Texas was all for it in 1836. The only hitch in the deal was that Texas had adopted a new state constitution that legalized slavery and banned free Blacks. That wasn't going to fly with the North.

Not willing to throw off the delicate balance of free and slave states and launch America into a Civil War, America passed on Texas. We were getting really good at dancing around the whole slavery issue again and again and again. 

Strangely, avoidance wasn't solving the issue.

More and more Americans flooded into Texas over the next nine years, and by 1845, the population of Americans in the territory had more than tripled. More Americans meant more and more settlers eager for adoption into the United States. When America finally did give in to the desire for Texas, it paired it with the acquisition of Oregon to balance out the question of slavery.

All of a sudden Mexico was like "What the what? Texas is ours." 


The war ended with American victory and a treaty that increased the nation's size by more than half a million square miles. Plus, the Oregon Territory was thrown in there, too, adding another quarter million square miles, creating a transcontinental nation-state. 

Another plus? Developments like the railroad, the telegraph, and the postal system were under way, fueling theories of Anglo-Saxon supremacy that fused with national pride to produce Manifest Destiny, the conviction that white Americans were divinely ordained to dominate the continent, from sea to shining sea.

Score, Manifest Destiny—and President James K. Polk's expansionistic campaign promises—was going well. 

Well, sort of well.

The issues that emerged with the acquisition of western lands, particularly in the Southwest, reawakened the sleeping giant of American politics: the controversy between North and South over slavery that most U.S. political leaders had spent a lifetime attempting to suppress. 

Though President Polk and Manifest Destiny embodied the spirit, adventure, and triumphalism of the period, they also paved the way for the splintering of the Union in 1861.

What is Manifest Destiny & Mexican-American War About and Why Should I Care?

A narrowly elected president. A controversial war. Sharp divisions over America's foreign and domestic policy and its future path. 

Sound familiar? If not, you might want to pause here and pick up a newspaper or two.

Regardless of how you feel about the current state of affairs in American politics, warfare, and foreign relations, elements of our national history can only enhance your perspective and broaden your understanding of the country's position and reputation in the world.

  • How did we come to be the way we are?
  • When and how did we assume the national borders that are now taken for granted on the colorful maps adorning almost every American classroom?

Study of the Mexican-American War and the expansionist policies of mid-19th-century United States can help answer these questions. Iraq and Vietnam weren't the first controversial wars in national history. The notion that everyone in the country once zealously supported the chief executive, regardless of his party or his agenda, is a myth.

Not every square inch of American territory was gained by bloodshed, and many powerful historical figures thought that the land we did acquire was actually insufficient. If they had their way, our country would look very different today. The United States would include parts—or all—of Mexico, Nicaragua, the rest of Central America, Cuba, and a few other places, to boot. 

So, what drove those ardent expansionists and why did they ultimately fail? 'Cause we'll tell you that most Americans did actually favor aggressive territorial acquisition.

Also keep in mind that in history, nothing can be taken for granted, and hindsight's always 20/20. Never assume that our country always looked the way it does today on a map, or—as in the ideology of Manifest Destiny—that we were destined to assume our present form. 

Newsflash: History doesn't neatly unfold according to a series of predetermined—or deterministic—prophecies. No matter how Americans have rationalized their land conquests, or whether they were fighting Mexicans, Native Americans, or others, these were messy, bloody, protracted battles on all sides.

The outcome was neither obvious nor easy. To trivialize the process of westward expansion or imperialism as an inevitability is to oversimplify history. Even if we now know the end of this particular story—that we did in fact conquer the continent, "from sea to shining sea"—it is the how and the why that really counts. The but is also pretty important. In other words, what was the cost of westward expansion?

You could think about that question in terms of the lives lost—white settlers on the frontier, American soldiers, Mexican soldiers, Mexican citizens, Native Americans—or the tribal cultures that were decimated by disease and bloodshed along the way. Or the price of the many land treaties in cold hard cash, the dramatic alterations to the landscape and the resultant changes in the environment, or the impact on national goals, values, and ideas. 

The Civil War must be part of that answer, too. Even if most 19th-century Americans agreed on the virtues of expanding the national boundaries westward, they disagreed violently over whether slavery should expand into the west as well.

Manifest Destiny & Mexican-American War Resources


K. Jack Bauer, The Mexican War, 1846–1848 (1974)
Bauer provides a detailed account of the politics surrounding the war and the battles that composed it. Note that this history is colored by the context in which it was written: the Vietnam War.

John S. D. Eisenhower, So Far from God: The U.S. War With Mexico, 1846–1848 (1989)
This is a well-researched and engaging history of the Mexican-American War and its implications for the Civil War, the figures involved, and the concept of Manifest Destiny.

Paul W. Foos, A Short, Offhand, Killing Affair: Soldiers and Social Conflict During the Mexican-American War (2002)
Foos emphasizes the soldiers' perspective by utilizing primary sources such as letters and diaries. He examines their interaction with broader themes such as Manifest Destiny, which some interpreted for themselves by raiding, pillaging, and raping across the Mexican countryside.

Robert W. Johannsen, To the Halls of the Montezumas: The Mexican War in the American Imagination (1985)
Johannsen's book represents a rich cultural history of the place and the significance that the war occupied in the minds of Americans who were, for the most part, far removed from the conflict.

David Potter, The Impending Crisis: 1848–1861, (1976)
Potter's famous Civil War pre-history is tellingly commenced with the end of the Mexican-American War and the Wilmot Proviso that plunged the nation into years of sectional debate that erupted at various times and places—and ultimately in 1861—in outright bloodshed and secession.

Charles Sellers, The Market Revolution: Jacksonian America, 1815–1846 (1991)
This is a very comprehensive examination of American antebellum society, with special attention devoted to political, economic, and religious aspects, and a thorough (and critical) assessment of the road to the Mexican-American War and its supporters.


Various Artists, The Music of the Wild West (2007)
Originally conceived of as an accompaniment for the 1993 television documentary on the Wild West, this collection features a wide array of 19th-century cowboy classics recorded by contemporary country stars like Lyle Lovett, Crystal Gayle, and Marty Stuart.

Various Artists, Voices from the Oregon Trail (2000)
Sing along to these spirited melodies from the original American road trip.

Various Artists, The West (1996)
The official soundtrack to director Ken Burns' documentary film, this disc offers old-time American favorites like "Git Along, Little Doggies" and "Amazing Grace," as well as a number of traditional Native American chants and prayers used to bring to life the world of the Wild West.

Dean Shostak, Davy Crockett's Fiddle (2002)
Musician Dean Shostak performs American classical compositions from the antebellum era using a fiddle that belonged to the 19th-century frontiersman Davy Crockett.


Young Hickory
James Knox Polk, a Jackson protégé known as "Young Hickory."

The Disputed Area
1833 map of Oregon Territory.

The Pacific Northwest
1846 map of Oregon Country, extending southward to California.

American Progress by John Gast
An allegorical painting from 1872. The author of a travel guide to the Pacific Coast commissioned this painting. The female figure was an allegory of Liberty—a popular iconic representation at the time—who wears the Star of Empire. She leads the white settlers, along with their transportation and communications technology (the railroad and telegraph cables) and their racial and intellectual enlightenment, into the West, as Native Americans, buffalo, and other animals retreat before her.

Texas Coming In by H. Bucholzer
Lithograph of a political cartoon. Published in New York by James Baillie, 1844. From the Prints and Photographs Division, Library of Congress.

Movies & TV

Ravenous (1999)
Australian actor Guy Pearce stars as Captain John Boyd, an American commanding officer during the Mexican-American War who's sent to defend Fort Spencer, a curious outpost deep in the Sierra Nevada mountain range. What happens when he and the other inhabitants encounter the mysterious lone survivor of an ill-fated frontier expedition?

500 Nations: Removal—War and Exile in the East (1995)
This episode of a six-part series on the deep and complex history of Native Americans follows the brutal Trail of Tears that led not only to the displacement of tens of thousands of families but also to the death of large portions of the Seminole, Chickasaw, Choctaw, Cherokee, and Creek populations.

How the West Was Won (1962)
This Oscar-winning saga traces American westward expansion during the mid-nineteenth century using the experiences of two migrant families. Henry Fonda and Carroll Baker star as leading members of the Prescott and Rawlings clans who venture west to find fortune and ultimately settle in California.

The Big Trail (1930)
Shot entirely on location in the rural Midwest, this classic bit of Western cinema pits wagon train pioneers against roving bands of murderous Native Americans and the hostile wilderness. That which would be considered a cliché today was then a widely accepted narrative of the Old West.

The Lash (1930)
This 1930s talkie delves into the often tumultuous relationship between American migrants and Spanish-speaking Californians in the immediate aftermath of the Mexican-American War.


Covering the Controversial War
This is a fantastic work-in-progress from Virginia Tech that explores the Mexican-American War and the media, which will provide "links to transcriptions of newspaper articles, indexes, images, bibliographies, timelines, and official documents related to the 1846–1848 war between the United States and Mexico."

Chronicling the Mexican-American War
PBS's site on the "U.S.-Mexican War," includes resources for educators, a timeline, and a series of biographies.

Contextualizing the Conflict
This site on the war developed by Descendants of Mexican-American War Veterans includes maps, documents, and other primary sources, as well as a list of historic sites in Texas, California, New Mexico, Colorado, Louisiana, and Mexico.

Military History
You can read "The Mexican War and After," extracted from American Military History: Army Historical Series.

Primary Sources on the War
Historical Text Archive; contains some broken links but those functioning include Pres. Polk's War Message to Congress and the text of the Treaty of Guadalupe Hidalgo.

Historical Documents

The Dark Horse's Inaugural
You can read James K. Polk's inaugural address from March 4th, 1845, available through the Avalon Project at Yale University.

Annexation Attempt
The failed Treaty for Annexing Texas, submitted to the Senate on April 22nd, 1844 and subsequently rejected on June 8th by a vote of 16 "ayes" to 35 "noes."

Successful Admission
The Congressional Joint Resolution admitting Texas into the United States, December 29th, 1845.

Requesting Recognition of War
President Polk's May 11th, 1846 message to a joint session of Congress on the state of relations between the United States and Mexico.

The Father of Civil Disobedience
You can read Henry David Thoreau's justification for his refusal to pay his taxes and his desire not "to be associated with Massachusetts, either in holding slaves or in conquering Mexico," in the online version of his work, A Week on the Concord and Merrimack Rivers.

Half of Mexico Becomes American Territory
The Treaty of Guadalupe Hidalgo from February 2nd, 1848 is available online.

The First American Occupation of a Foreign Capital
Army military historians have chronicled the dramatic events surrounding the American occupation of Mexico City, with some valuable maps and contextualization of the situation in Mexico when hostilities began.

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