On this day in 1848, the Treaty of Guadalupe Hidalgo is signed, ending the Mexican-American War in favor of the United States. The Treaty of Guadeloupe Hidalgo added an additional 525,000 square miles to United States territory, including the area that would become the states of Texas, California, Nevada, Utah, New Mexico and Arizona, as well as parts of Colorado and Wyoming. Controversy during and after the war pitted President James K. Polk in a political war against two future presidents: Zachary Taylor and Abraham Lincoln.
Polk, a Democrat, ignited the Mexican-American War when he sent his Commanding General of the Army Zachary Taylor and his troops to claim territory along the Rio Grande River between the U.S. and Mexico. Polk insisted Mexico had invaded the U.S. when an earlier skirmish between American and Mexican troops erupted over the ill-defined territorial boundaries of Texas. Polk's action was immediately denounced by Abraham Lincoln, then a leading Whig member of Congress, who described the resulting war as unconstitutional, unnecessary and expensive. While Taylor performed his military duty in Texas, Polk wrestled with Congressional opposition led by Lincoln in Washington.
Polk was a firm believer in America's "Manifest Destiny" of increased U.S. territorial expansion in order to bring democracy and Protestant Christianity to a "backward" region. Lincoln and his cohorts protested not so much expansionism itself, but Polk's justification of the war. Although the war ended favorably for the U.S., Lincoln continued to attack Polk after the signing of the treaty for his lack of an exit strategy that clearly defined citizenship and property rights for former Mexican citizens. Lincoln called the president "a bewildered, confounded, and miserably perplexed man." Although Polk's war was successful, he lost public support after two bloody years of fighting during which the U.S. lost 1,773 men and spent a whopping $100 million.
Meanwhile, Taylor earned national popularity for his heroic actions during the war and for the camaraderie he shared with even his lowliest subordinates. When the war ended, Taylor decided to run for the presidency. One of his political mentors happened to be Abraham Lincoln, who wrote a note to Taylor after the war ended advising him of what he ought to say regarding the Mexican-American War and the question of slavery in any newly won territories. Lincoln suggested that Taylor should declare "we shall probably be under a sort of necessity of taking some territory; but it is my desire that we shall not acquire any extending so far south as to enlarge and aggravate the distracting question of slavery."
Polk chose not to run again for the presidency, and Taylor barely won the popular vote in a race that included former President Martin Van Buren and Democratic nominee Lewis Cass. Van Buren, the Free-Soil Party candidate and former Democrat, acted as a spoiler, siphoning off Democratic votes that would likely have gone to Cass. Unfortunately for Lincoln, Taylor and his immediate successors failed to address the issue of slavery during their terms, leaving the question to Lincoln to solve over a bloody civil war a decade later.