Which U.S. President was in office during the Mexican-American War?

James Polk was the U.S. President during the Mexican-American War, which lasted from 1846 to 1848. Polk's administration was characterized by a strong belief in Manifest Destiny, the idea that the United States was destined to expand across the continent. He advocated for the annexation of Texas and sought to acquire California and New Mexico, which were then part of Mexico. The war was partly a result of the U.S. desire to expand its territory, and Polk played a significant role in its initiation by sending troops to disputed territories, which led to armed conflict.

Polk's leadership during this period significantly shaped the territorial boundaries of the United States, which were solidified with the Treaty of Guadalupe Hidalgo, concluding the war and ceding large portions of land from Mexico to the U.S. This expansion reinforced the notion of Manifest Destiny and had profound implications for the nation's development, leading to both significant economic opportunities and heightened sectional tensions regarding slavery.