The Mexican–American War (1846–1848)

A Turning Point in North America

The Mexican–American War was a major conflict between the United States and Mexico that took place from 1846 to 1848. It changed the map of North America and had long-lasting effects on both countries. For students of English, this war is an important topic for learning vocabulary about history, geography, and government.

Background and Manifest Destiny

In the early 1800s, the United States was growing quickly. Many Americans believed in “Manifest Destiny”, the idea that the United States had a mission to expand west from the Atlantic Ocean to the Pacific Ocean. At the same time, Mexico controlled a huge area of land, including what is now Texas, California, New Mexico, Arizona, Nevada, Utah, and parts of Colorado and Wyoming.

Tension began when American settlers moved into Texas, which was part of Mexico. The settlers did not always follow Mexican laws, and cultural differences caused disagreements. In 1836, Texas fought a war for independence and became its own country, the Republic of Texas. When the United States decided to annex (add) Texas in 1845, Mexico was angry and saw this as a threat.

The Road to War

The immediate cause of the war was a border dispute. The United States said the border between Texas and Mexico was the Rio Grande River, but Mexico said it was farther north, at the Nueces River. When U.S. soldiers entered the disputed area, Mexican troops attacked them. President James K. Polk used this event to ask Congress to declare war, saying that American blood had been shed on American soil.

Battles and the Treaty of Guadalupe Hidalgo

The war was fought in several regions. In the west, American forces quickly took control of California and New Mexico. In northern Mexico, U.S. troops won important battles at Monterrey and Buena Vista. The most dramatic part came when American soldiers landed at Veracruz on the Gulf of Mexico and marched toward Mexico City. After several battles, they captured the Mexican capital in September 1847.

The war ended in 1848 with the Treaty of Guadalupe Hidalgo. Under this treaty, Mexico agreed to give up a large area of land—about half of its territory—to the United States. This land, called the Mexican Cession, included present-day California, Nevada, Utah, most of Arizona, and parts of New Mexico, Colorado, and Wyoming. In return, the United States paid Mexico $15 million and promised to protect the rights of Mexican citizens living in the new territory.

Long-Term Effects

The Mexican–American War had many long-term effects. The United States gained valuable land and resources, which helped it grow into a larger and stronger nation. However, the new territory also created problems. Arguments about whether slavery should be allowed in the new lands increased tension between the North and the South and brought the United States closer to the Civil War.

For Mexico, the war was a painful loss of land and national pride. At the same time, it led some Mexicans to work harder to strengthen their government and national identity. Today, the Mexican–American War remains an important event that shaped the borders, politics, and future of both countries.

Comprehension Questions

1. What was “Manifest Destiny,” and how did it influence the United States?
2. Why was Mexico upset when the United States annexed Texas?
3. What disagreement about the border helped start the war?
4. What did Mexico lose and what did the United States gain in the Treaty of Guadalupe Hidalgo?
5. How did the results of the war affect future events in the United States and Mexico?