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. Yet as the number of slaves and the size of plantations grew, planters also sought to impose stricter controls over blacks, enslaved and free, and to bind non-slaveowning whites more firmly to their interests. Enslaved blacks, meanwhile, developed an increasingly rich culture by combining traditions and rituals from Africa and the Caribbean with U.S. customs and beliefs. This African American culture served as one form of resistance against slavery’s brutality. Many enslaved laborers resisted in other ways as well: sabotaging tools, feigning illness, running away, or committing arson or theft. Smaller numbers engaged in outright rebellions.

While most white Northerners were willing to leave slavery alone where it already existed, many hoped to keep it out of newly acquired territories. In this sense, the removal of the Cherokee did not disturb Northerners since it was largely yeoman farmers who would benefit from access to their land. Instead, many northern whites opposed removal on moral grounds. When it came to the Mexican-American War, however, more Northerners—black and white—feared victory would mainly benefit southern planters. The vast lands gained from Mexico in 1848 intensified the debates over slavery and led small but growing numbers of white Northerners to join African Americans, 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.

It was the panic of 1837, however, that opened the way for a new political alignment. The extended depression allowed the newly formed Whig Party to gain support for its economic and reform agenda. In 1840 Whigs captured the White House and Congress, and a new antislavery force, the Liberty Party, emerged as well. But just four years later, James K. Polk’s support of westward expansion and manifest destiny returned Democrats to power. The political volatility continued when the U.S. victory in the war with Mexico intensified debates over slavery in the territories, fracturing the Democratic Party and inspiring the founding of the Free-Soil Party.

Political realignments continued over the next decade, fueled by growing antislavery sentiment in the North and proslavery beliefs 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 a divine blessing. 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.