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Mexican-American War

History >> Westward Expansion

The Mexican-American War was fought between the United States and Mexico from 1846 to 1848. It was primarily over the territory of Texas.


Texas had been a state of the country of Mexico since 1821 when Mexico gained its independence from Spain. The Texans, however, began to disagree with the government of Mexico. In 1836, they declared their independence from Mexico and formed the Republic of Texas. They fought several battles including The Alamo. In the end, they gained their independence and Sam Houston became the first President of Texas.

Texas Becomes a US State

In 1845, Texas joined the United States as the 28th state. Mexico didn't like that the United States took over Texas. There also was a disagreement over the border of Texas. Mexico said the border was at the Nueces River while Texas claimed the border was further south at the Rio Grande River.

War with Mexico

President James K. Polk sent troops to Texas to protect the border. Soon Mexican and US troops were shooting at each other. On May 13, 1846 the United States declared war on Mexico.

Map of the Mexican American War
Mexican-American War Overview Map
By Kaidor [CC BY-SA 3.0 (],
via Wikimedia Commons
(Click picture to see larger view)

The Mexican army was led by General Santa Anna. The US forces were led by General Zachary Taylor and General Winfield Scott. General Taylor's forces were the first to engage the Mexican army. They fought an early battle at Palo Alto where the Mexicans were forced to retreat.

General Taylor advanced into Mexico fighting battles at the city of Monterrey and a mountain pass called Buena Vista. At the Battle of Buena Vista, Taylor and 5,000 troops were attacked by 14,000 Mexican troops led by Santa Anna. They held off the attack and won the battle despite being outnumbered.

Capture of Mexico City

President Polk didn't trust Zachary Taylor. He also considered him a rival. Instead of reinforcing Taylor's troops to capture Mexico City, he sent in another army led by General Winfield Scott. Scott advanced on Mexico City and captured it in August of 1847.

Mexico City during the Mexical American War
Fall of Mexico City during the Mexican-American War
by Carl Nebel

Treaty of Guadalupe Hidalgo

With the United States in control of their capital city and much of the country divided, the Mexicans agreed to a peace treaty called the Treaty of Guadalupe Hidalgo. In the treaty, Mexico agreed to the border of Texas at the Rio Grande. They also agreed to sell a large area of land to the United States for $15 million. Today this land makes up the states of California, Nevada, Utah, and Arizona. Portions of Wyoming, Oklahoma, New Mexico, and Colorado were also included.

Mexican Cession in Mexican View
from the U.S. Government

Interesting Facts about the Mexican-American War
Westward Expansion
California Gold Rush
First Transcontinental Railroad
Glossary and Terms
Homestead Act and Land Rush
Louisiana Purchase
Mexican American War
Oregon Trail
Pony Express
Battle of the Alamo
Timeline of Westward Expansion
Frontier Life
Daily Life on the Frontier
Log Cabins

People of the West
Daniel Boone
Famous Gunfighters
Sam Houston
Lewis and Clark
Annie Oakley
James K. Polk
Thomas Jefferson
Works Cited

History >> Westward Expansion

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