Some historians have called the Mexican War the first battle of the Civil War, for it revived intense and heated debate about the expansion of slavery in the West. Tensions came to a head when Pennsylvanian congressman David Wilmot set forth the Wilmot Proviso in 1846, proposing that slavery be banned in the West. Not surprisingly, Southerners killed the proviso in the Senate before it could become law.
Nonetheless, the damage had been done, and expansion of slavery remained the hot topic in the election of 1848 . The Whigs nominated war hero General Zachary Taylor on a rather noncommittal platform (they didn’t want to lose Southern votes), while the Democrats nominated Lewis Cass. Hoping to appeal to voters from both regions, Cass proposed applying popular sovereignty to the slavery question, arguing that the citizens living in each territory should decide for themselves whether theirs would become a slave state or a free state. Taylor won the election, but he died after only sixteen months in office, and Vice President Millard Fillmore became president in 1850.
The Compromise of 1850
Because Taylor and Fillmore had never made their views on slavery in the West clear, the issue remained unresolved. When California applied for admission as a free state, the debate picked up right where it had left off. In Congress, heavyweights Daniel Webster and Henry Clay met for the last time to hammer out a compromise. After much debate, the North and South finally came to an agreement that both sides thought would be lasting and binding.
There were five components to this Compromise of 1850 . First, California would be admitted as a free state. Second, popular sovereignty would determine the fate of the other western territories. Third, Congress would cancel some of Texas’s debts and, in exchange, give some of Texas’s western land to New Mexico Territory. Fourth, slave trading would be banned in Washington, D.C. Finally, Congress would pass a tougher Fugitive Slave Law, to reduce the number of slaves who escaped to the North and Canada every year. Although Southerners had not conceded a lot in making the bargain, Northerners were still offended by the new law, and many refused to obey it.
Pierce and Expansion
The pro–Southern Democrat Franklin Pierce replaced Fillmore after defeating Whigs and Free-Soilers in the election of 1852. Playing off manifest destiny and the Southern desire for new slave states, Pierce supported a variety of proposals to acquire more territory. He tacitly supported adventurer William Walker’s attempt to annex Nicaragua but backed off after Walker was deposed and executed. Pierce also investigated the possible acquisition of Cuba from Spain, but the plan backfired after his machinations were leaked to Northerners in the Ostend Manifesto. More productively, he sent the U.S. Navy to Japan to open trade negotiations and bought a small strip of land in present-day Arizona and New Mexico in the 1853 Gadsden Purchase.
The Kansas-Nebraska Act
Hoping to attract railroad development through the North, Illinois Senator Stephen Douglas introduced the Kansas-Nebraska Act in 1854 and pushed it successfully through Congress. The act carved the territory into the Kansas and Nebraska territories and, more controversially, declared that popular sovereignty would determine the future of slavery there.