Securing the Southwest:The Northern Pursuit of Texas, New Mexico, and California Daniel J. Burge (bio) Click for larger view View full resolution This image humorously depicts the Democratic Party's strategy to win the election of 1844. Northern Democrats saw the annexation of Texas as a winning partisan issue to use against their Whig rivals and a development that would be beneficial to the whole nation, not just the South. Library of Congress Prints and Photographs Division, https://www.loc.gov/pictures/resource/cph.3a15078/ [Dec. 21, 2022]. [End Page 416] In September 1847 in Pittsburgh, Pennsylvania, Vice-President George Mifflin Dallas delivered an address on the U.S.–Mexico War defending President James K. Polk. After arguing that Mexico was to blame for starting the conflict, Dallas explored another question: "If, upon the conclusion of a treaty with Mexico, we should come into possession of one-half or two-thirds of her territory—what are we to do with it?" Although the outcome of the war was uncertain, Dallas remained confident that the United States would be able to seize a portion of Mexico—indeed that the United States was destined to obtain most of Mexico. "Of one thing we are quite certain," Dallas declared, "—the Yankees will in time overrun that portion of their territory; and though there is much Mexican blood upon it, we may look to the period . . . when a number of large States, stretching from the Gulf of Mexico to the Pacific ocean, will be distinguished in the constellation of our Union."1 Dallas was a northern man, speaking to a northern audience who believed that the future United States would include territory stretching from the Pacific to the Gulf of Mexico. Although historians have spent a great deal of time examining why antebellum southerners dreamed of acquiring what became the American Southwest, they have not adequately explained why northerners held similar views. On the rare occasions when historians have examined northern expansionists, they have generally [End Page 417] studied Stephen Douglas and the Young America movement.2 In contrast, then, this essay explores expansionists from New York and Pennsylvania who were not allies of Stephen Douglas or affiliated with Young America. By focusing on prominent northern expansionists such as George Mifflin Dallas, Daniel Dickinson, and James Buchanan and drawing on New York and Pennsylvania newspapers, this essay shows that not only did enthusiasm for territorial expansionism exist outside of the South, it was also to be found among older members of the Democratic Party. Indeed, it was the men whom the Young Americans would deride as "Old Fogys" who helped shepherd through the annexation of Texas and the Treaty of Guadalupe Hidalgo and who would introduce popular sovereignty into political discourse.3 Northerners played a key role in securing the Southwest for the United States, but they embraced expansionism for different reasons than their southern peers. First, northern Democrats such as James Buchanan and George Mifflin Dallas routinely stressed the economic benefits to be gained from expansion. Northern manufactures, they argued, would find new markets if the United States acquired the lands stretching from Texas to California. In addition, they denied that expansion would empower enslavers. Texas, they argued, would weaken the institution of slavery, as it would drain the enslaved population out of the border states. A few years later, these same northern expansionists cobbled together the idea of popular sovereignty and argued that slavery, even if permitted in territories seized from Mexico, would never flourish. Linking expansion to national greatness, they believed the United States could gobble up territory without increasing sectional tension. These northern Democrats were not "northern men with southern loyalties," or "doughfaces," but were rather [End Page 418] traditional Jacksonian Democrats who believed in the beneficial effects of territorial expansion. Unwilling to accept that North and South would ever come to blows over slavery, they unwittingly propelled the United States toward a conflict by helping to vastly expand the boundaries of the young nation. Nobody championed expansion more earnestly than Robert John Walker.4 Born and raised in Pennsylvania, Walker came from a well-connected family and graduated from the University of...