By the mid-nineteenth century, the United States stood at a crossroads. Most Americans considered expansion advantageous and critical to revitalizing the economy. Planters believed it was vital to slavery’s success. While most white Northerners were willing to leave slavery alone where it already existed, many hoped to keep it out of newly acquired territories. The vast lands gained from Mexico in 1848 intensified these debates. Between 1830 and 1850, small but growing numbers of Northerners joined slaves, American Indians, and Mexicans in protesting U.S. expansion. Even some yeomen farmers and middle-class professionals in the South questioned whether extending slavery benefited the region economically and politically. But these challenges remained limited until 1848, when the fight over slavery in the territories fractured the Democratic Party, created a crisis for the Whigs, and inspired the growth of the Free-Soil Party.
Political realignments continued over the next decade, fueled by growing antislavery sentiment in the North and proslavery ideology in the South. In 1853 Solomon Northrup horrified thousands of antislavery readers with his book Twelve Years a Slave, which vividly described his life in bondage. Such writings alarmed planters like James Henry Hammond, who continued to believe that slavery was “the greatest of all the great blessings which Providence has bestowed upon our glorious region.” Yet in insisting on the benefits of slave labor, the planter elite inspired further conflict with Northerners, whose lives were increasingly shaped by commercial and industrial developments and the expansion of free labor.