Mexican War

"Battle of Buena Vista," Carl Nebel, 1851

“All the battles of the Mexican war had been fought before Mr. L. took his seat in congress, but the American army was still in Mexico …”Lincoln autobiography, 1860

Sectional tensions rose to the surface of American politics during the 1840s, as the international frontier moved far from the Old Northwest. The United States expanded to Texas, Oregon, and California by the end of the decade, and disputes about the extension of slavery into these areas could no longer be avoided. The nation’s enthusiasm about expansion — most famously captured by the term “manifest destiny” — tended to overtake resistance, mainly from within the Whig Party.

Much of the attention focused on the border between Mexico and Texas, where a political movement led largely by Anglo-American settlers declared independence from Mexico in 1836. In the United States, advocates of expansion helped elect James Polk, Democrat of Tennessee, to the presidency in 1844. The following year, Texas was admitted to statehood and the Mexican government, which remained reluctant to recognize an independent Texas, broke off diplomatic relations with the United States government. Joining in the ongoing border dispute between Texas and Mexico, Polk sent General Zachary Taylor and U.S. troops to the Nueces River line. At the same time, Polk made plans to seize Californian ports if Mexico declared war. In January of 1846, Polk ordered Taylor to begin moving his troops into the disputed area to the Rio Grande, and weeks after they arrived there in March, the U.S. Congress declared war on Mexico.

U.S. troops fought battles along three major lines of attack, including a large-scale marine invasion at the port of Vera Cruz. Military success propelled the U.S. Army into an occupation of central Mexico that lasted for months. The February 1848 Treaty of Guadalupe Hidalgo ended the war, with Mexico ceding California and New Mexico to the United States in return for fifteen million dollars. The acquisition of these lands exacerbated the divisions over slavery’s expansion westward. 

In December 1847, Abraham Lincoln took his seat as an Illinois Representative in the U.S. Congress. Combat had ended, and the U.S. military had been occupying the Mexican capital for three months when, on December 22, 1847, Lincoln introduced a series of resolutions demanding that President Polk identify the spot where the fighting began and answer whether this spot belonged to Texas or to Mexico. These resolutions earned Lincoln the nickname “Spotty Lincoln.” More than ten years later, during the race for the Illinois Senate seat, Stephen Douglas ridiculed Lincoln with references to these spot resolutions.