On the causation of the Mexican-American War

In 1844, Whig, former President, and then-Representative John Quincy Adams reflected on President John Tyler’s bill to annex Texas, writing about his anxiety over “the degeneracy of my country… under the transcendent power of slavery and the slave-representation.” Adams celebrated the treaty’s failure later that year, praising the nation’s escape from “slave-tainted monarchy, and of extinguished freedom.” In 1847, in the midst of the Mexican-American War, Reverend John Dudley of Vermont gave a fiery sermon in which he excoriated “the two leading sins of this nation, SLAVERY AND WAR.” Reverend Dudley continued, claiming “that the present war has its origin and justification in the slave-holding interest in these United States.” In early 1848, right before the war’s conclusion, former enslaved man and intellectual Frederick Douglass gave a speech calling the war nothing less than a “slaveholding crusade.” All three of these men, and many more people across the United States, were united in their denunciation of the Mexican-American War as one instigated by the slaveholding interests of the country in order to expand slavery westward and ensure that the institution continued to enjoy economic and political benefit. This accusation, however, lacks consensus, as others such as President James K. Polk, Ulysses S. Grant, and Mississippi Senator Robert J. Walker argued that the war’s causation lay in such varied reasons as Mexican debt owed to the United States and its citizens, a simple desire for more land to settle, or a belief that if the United States did not seize valuable land from the weak Mexican state, the British would. Therein lies the question this thesis will answer: Did slaveholders and slavery’s advocates instigate the Mexican-American War to benefit themselves, or is the role of slavery in uniting pro-war feelings overstated? If slavery’s role is overstated, what lies behind the United States’s decisions to annex Texas, inherit a border dispute, and provoke the Mexicans into war? To uncover whether slaveholding interests instigated the Mexican-American War, I will examine the leadup to the war, most notably the circumstances that led the United States to annex Texas, and how different people and groups perceived the choices being made in Washington and Mexico City. Then, the war itself and how a calcifying political establishment led to such incidents as the Wilmot Proviso, which thrust the debate over slavery’s connection to the war to the forefront. Finally, an examination of the war’s end and how victory was interpreted on both sides of the new border. I will describe the perspectives of the major political parties, Whigs and Democrats, from North and South, the servicemen who fought the war, and the civilians who saw, wrote, and argued about the war. Though I primarily explore American perspectives, some translated Mexican documents offer a broader understanding of the war that extends interpretations to the invaded as well as the invader