What Was the Mexican-American War History?

The Mexican-American War was a significant conflict that took place between 1846 and 1848. This war was fought between the United States and Mexico over territorial disputes, which eventually led to the annexation of Texas by the United States. The war had far-reaching consequences for both nations, with the United States becoming a dominant power in North America and Mexico losing vast territories.


The origins of the Mexican-American War can be traced back to the Texas Revolution of 1835-1836. At that time, Texas was a part of Mexico, but American settlers had started to move into the region, lured by cheap land and economic opportunities. However, tensions between American settlers and Mexican authorities soon boiled over into open conflict, resulting in the establishment of an independent Republic of Texas.

Texas Annexation

In 1845, after several years as an independent republic, Texas was annexed by the United States. This move infuriated Mexico, which still considered Texas as its own territory. The Mexican government refused to recognize the independence of Texas and prepared for war with the US.

Outbreak of War

The first shots of the Mexican-American War were fired on April 25, 1846 when a detachment of US soldiers clashed with Mexican troops near the Rio Grande River. President James K. Polk used this incident as a pretext for declaring war on Mexico.

The Course of War

The US forces quickly gained ground in northern Mexico, capturing Monterrey and Buena Vista in early battles. However, despite initial setbacks, Mexican forces under General Santa Anna managed to launch counterattacks at Cerro Gordo and Contreras.

Treaty of Guadalupe Hidalgo

In September 1847, US forces led by General Winfield Scott captured Mexico City after a grueling siege. The capture of the Mexican capital effectively ended the war, and negotiations for peace began. The Treaty of Guadalupe Hidalgo was signed on February 2, 1848, which recognized Texas as part of the US and ceded vast territories to the US, including California, Nevada, Utah, Arizona, New Mexico, and parts of Colorado, Wyoming, Kansas, and Oklahoma.


The Mexican-American War had far-reaching consequences for both nations. For the United States, it marked a significant expansion of its territory and established its dominance in North America. However, it also exacerbated tensions between the North and South over the issue of slavery in newly acquired territories.

Mexico suffered a severe blow to its national pride and lost nearly half of its territory in the war. It also led to a period of political instability in Mexico that lasted for decades.


In conclusion, the Mexican-American War was a defining moment in American history that had significant consequences for both nations involved. It was fought over territorial disputes but ultimately resulted in the expansion of American power and weakened Mexico’s position as a regional power. Despite being over 150 years ago, this conflict still has lasting implications for both countries today.