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1846-1848Primary source · 2 sourcesWell documented

Manifest Destiny and the Mexican-American War

A war of conquest gives the United States its Pacific coast and half of Mexico

On the timeline · around 1846-1848 · Founding and Early RepublicFounding and Early RepublicCivil War and ReconstructionManifest Destiny and the Mexican-American War18201830184018501860

Quick facts

War years
1846-1848
Ended by
Treaty of Guadalupe Hidalgo, February 2, 1848
Territory ceded
55 percent of Mexico's territory
Payment
$15 million

What happened

In the 1840s many Americans embraced the ideology of manifest destiny, the belief that the United States was destined to extend its nation across the continent. Acting on that impulse, and after the annexation of Texas, the United States in 1845 embarked on what the State Department's own history calls its first offensive war by invading Mexico. The Mexican-American War ended with the Treaty of Guadalupe Hidalgo, signed on February 2, 1848, by which Mexico ceded 55 percent of its territory, including present-day California, Nevada, and Utah and parts of Arizona, New Mexico, Colorado, and other states. The United States paid Mexico $15 million and extended its boundaries west to the Pacific Ocean.

Why it matters

The war gave the United States its Pacific coastline and the Southwest, completing the continental expansion begun with Louisiana, and the discovery of gold in newly acquired California the same year drew hundreds of thousands west. It also handed the country an enormous new territory whose status, free or slave, reignited the sectional crisis and helped set the stage for the Civil War.

How we know

The Treaty of Guadalupe Hidalgo survives in the National Archives with its terms of cession and payment, and the war and the ideology of manifest destiny are documented across U.S. and Mexican government records of the 1840s.

Sources

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Part of a timelineHistory of the United States32 events · A hundred English colonists on a swampy island, a constitution argued out over one Philadelphia summer, a country that doubled its size for four cents an acre and fought a civil war over who counted as free, and the superpower that came out the other sideView all →
Manifest Destiny and the Mexican-American War · History of the United States · SourcedStory