Name one war fought by the US in the 1800s.

The Mexican-American War is one of the significant conflicts fought by the United States in the 1800s, specifically from 1846 to 1848. This war was primarily the result of territorial expansion and the annexation of Texas, which had gained independence from Mexico in 1836. The U.S. desired further expansion westward, leading to conflict with Mexico over disputed territories.

As a result of the war, the United States acquired a large portion of Mexico's northern territories through the Treaty of Guadalupe Hidalgo, including present-day California, Nevada, Utah, Arizona, and parts of Colorado and New Mexico. This expansion played a crucial role in shaping the modern borders of the United States and had lasting effects on the nation's growth and its relationship with Mexico. The Mexican-American War is an essential topic in understanding U.S. history and its territorial development during the 19th century.