The 1848 treaty with Mexico did not bring the United States domestic peace. Instead, the acquisition of new territory revived and intensified the debate over the future of slavery in the western territories, widening the growing political and social division between North and South and leading to the creation of new single-issue parties.

Increasingly, the South came to regard itself as under attack by radical Northern abolitionists, and many Northerners began to speak ominously of Southern attempts to dominate American politics for the purpose of protecting enslavers’ human property. As tensions mounted and both sides hurled accusations, national unity frayed. Compromise became nearly impossible and antagonistic sectional rivalries replaced the idea of a unified, democratic republic.

The Liberty Party and the Wilmot Proviso

Committed to protecting White workers by keeping slavery out of the lands taken from Mexico, Pennsylvania Congressman David Wilmot attached an amendment that would prohibit slavery in the new territory to an 1846 revenue bill. The Wilmot Proviso was not entirely new. Other congressmen had drafted similar legislation, and Wilmot’s language was largely copied from the 1787 Northwest Ordinance that had banned slavery in that territory. His ideas were very controversial in the 1840s, however, because his proposals would prevent American slaveholders from bringing their enslaved people into the western territories, thus preventing them from settling there unless they were willing to work the land themselves. It would have also canceled out the Missouri Compromise of 1820 by banning slavery below the 36° 30′ parallel line, which was meant to be an area that was open to slavery. The measure passed the House but was defeated in the Senate.

When President James Polk tried again to raise tax revenue the following year (under the Treaty of Guadalupe-Hidalgo, Mexico had ceded the land in exchange for over $16 million from the U.S.), the Wilmot Proviso was reintroduced, this time calling for the prohibition of slavery not only in the Mexican Cession territory but in all U.S. territories. Once again, the revenue bill passed but the proviso was removed.

Political Divisions

That Wilmot, a loyal Democrat, should attempt to counter the actions of a Democratic president hinted at the party divisions that were to come. The 1840s were a particularly active time in the creation and reorganization of political parties and constituencies, mainly because of discontent with the positions of the mainstream Whig and Democratic Parties in regard to slavery and its extension into the territories. The first new party, the small and politically weak Liberty Party was founded in 1840 as a single-issue party, as were many of those that followed it. Its members were abolitionists who fervently believed slavery was evil and should be ended, and that this was best accomplished by political means.

Anti-Slavery vs. Abolition

The Wilmot Proviso captured the “anti-slavery” sentiments during and after the Mexican War. Anti-slavery advocates differed from the abolitionists. While abolitionists called for the end of slavery everywhere, anti-slavery advocates did not challenge the presence of slavery in the states where it already existed. Those who supported anti-slavery fervently opposed its expansion westward because they believed that slavery would degrade White labor and reduce its value, cast a stigma upon hard-working Whites, and deprive them of a chance to advance economically. The western states and territories, they argued, should be open to White men only—small farmers and urban workers for whom the West held the promise of economic advancement. Where slavery was entrenched, according to antislavery advocates, there was little land left for small farmers to purchase, and such men could not compete fairly with slaveholders who owned large plantations and dozens or hundreds of slaves. Ordinary laborers suffered also; no one would pay a White man a decent wage when a slave or an immigrant worked for next to nothing.

David Wilmot: anti-slavery or abolitionist?

Figure 1. David Wilmot, Democratic Congressman from Pennsylvania.

David Wilmot seemingly made his position on slavery clear when he spoke before the House and stated:

“I plead the cause and the rights of white freemen [and] I would preserve to free white labor a fair country, a rich inheritance, where the sons of toil, of my own race and own color, can live without the disgrace which association with negro slavery brings upon free labor.”^[1]

However, Wilmot certainly seemed to think that slavery would not be a permanent feature of American society. Whether or not Wilmot hoped that slavery would eventually end, he believed that it “carried the seeds of its own destruction” and that “its existence can only be perpetuated by constant expansion.”^[2]

Presumably, Wilmot was a supporter of Capitalist free-labor before anything else and this informed his attitudes toward slavery.

Can you think of any modern connections with Wilmot’s perspective and arguments against immigration today?

Wilmot opposed the extension of slavery into the Mexican Cession not because of his concern for Black slavery, but because of his belief that slavery hurt White workers, and that lands acquired by the government should be used to better the position of White American small farmers and laborers. Wilmot and his supporters argued that work was not simply something that people did, it gave them dignity and purpose, but in a slave society, labor had no dignity because it could be cheap and forced rather than paid and freely given. In response to these arguments, Southerners maintained that laborers in Northern factories were treated worse than enslaved laborers. Their work was tedious and low-paying and their meager income was spent on inadequate food, clothing, and shelter. There was no dignity in such a life. In contrast, they argued, Southern slaves were provided with a home, the necessities of life, and the protection of their masters. Factory owners did not care for or protect their employees in the same way. Wilmot and other free-labor advocates clung to the notion that Northern factory workers had the freedom to leave a job at any time and seek economic advancement elsewhere (like the western territories), however, this idea was predicated on the idea that factory workers were able to obtain enough money to pay for the journey west, which was rarely the case.

Try It

The Free Soil Party and the Election of 1848

The Barnburners vs. the Hunkers

Figure 2. This political cartoon depicts Martin Van Buren and his son John, both Barnburners, forcing the slavery issue within the Democratic Party by “smoking out” fellow Democrat Lewis Cass on the roof. Their support of the Wilmot Proviso and the new Free-Soil Party is demonstrated by John’s declaration, “That’s you Dad! more ‘Free-Soil.’ We’ll rat ‘em out yet. Long life to Davy Wilmot.”

At the 1848 New York State Democratic convention, anti-slavery supporters spoke in favor of the Wilmot Proviso, led by former President Martin Van Buren, who had lost his bid for reelection to James Polk in 1844. These anti-slavery folks were called Barnburners because they were thought to be willing to destroy all banks and corporations, in order to root out their abuses, just like farmers who were willing to burn down their own barn to get rid of a rat infestation.

Their opponents within the Democratic party, known as Hunkers, refused to support it. Angered, the Barnburners organized their own convention, where they chose anti-slavery, pro–Wilmot Proviso delegates to send to the Democratic national convention in Baltimore.

At the national convention, there were sets of delegates from both sides—the pro-Proviso ones chosen by the Barnburners and the anti-Proviso ones chosen by the Hunkers. When it came time to vote for the Democratic presidential nominee, the majority of votes were for Lewis Cass, an advocate of the popular sovereignty rule, wherein new states and territories would choose whether to allow slavery within their borders. Theoretically, this doctrine would allow slavery to become established in any U.S. territory, including those from which it had been banned by earlier laws.

Disgusted by the result, the Barnburners united with anti-slavery Whigs and former members of the now-defunct Liberty Party to form a new organization: the Free-Soil Party, which took as its slogan “Free Soil, Free Speech, Free Labor, and Free Men.” The party had one real goal—to oppose the extension of slavery into the territories. In the minds of its members and many other northerners of the time, southern enslavers had marshaled their wealth and power to control national politics for the purpose of protecting the institution of slavery and extending it into the territories. Many in the Free-Soil Party believed in the far-reaching conspiracy of the slaveholding elite controlling both foreign affairs and domestic policies as a scheme that came to be known as the Slave Power.

The Free-Soil Party

The new Free-Soil party promptly selected Martin Van Buren as its presidential candidate. For the first time, a national political party committed itself solely to the goal of stopping the expansion of slavery. Alongside Van Buren on the Presidential ticket were the Democratic nominee Lewis Cass and the Whig nominee General Zachary Taylor (James Polk did not run for a second term, having promised the Democrats who opposed his nomination in 1844 that he would only serve four years). Van Buren and the Free-Soil Party made a strong showing, winning 10% of the popular vote, while Taylor took the presidency with 47.3% of the votes, and Cass received 42.5%. With the Democratic vote split between Van Buren and Cass, Taylor won easily. His popularity with the American people and his heroism during the Mexican-American War served him well.

Taylor was chosen by the Whigs as a desperate last-ditch attempt to regain control of the Presidency, which they had not held since 1840. He had never held political office before, had little interest in the Presidency, and was reluctant to even label himself a Whig. The party leaders hoped that Taylor’s success as a military commander and his status as a enslaver from Louisiana might convince Southern Democrats to vote for him instead of the anti-slavery Free-Soil Van Buren or the popular sovereignty Cass, even though Taylor did not push for the expansion of slavery and leaned more toward popular sovereignty himself. The Whigs’ ultimate hope was that Taylor, through reputation alone, could combat the recent success of Polk in securing the Mexican Cession.

The Free Soil Party’s platform bridged the eastern and western leadership together and called for an end to slavery in Washington, D.C., and a halt on slavery’s expansion in the territories. In the 1848 election, Free-Soil Party candidates won over a dozen House seats and even managed to win one Senate seat in Ohio, which went to Salmon P. Chase. In Congress, Free Soil members had enough votes to swing power to either the Whigs or the Democrats, depending on which one aligned with their anti-slavery platform.

The upheavals of 1848 came to a quick end. Zachary Taylor was in office for only a little over a year when he died suddenly from a stomach ailment in 1850. During Taylor’s brief administration, the fruits of the Mexican-American War began to spoil. Increased clamoring for the admission of California, New Mexico, and Utah as states pushed the country closer to the edge. Gold had been discovered in California, and as thousands continued to pour onto the West Coast and through the trans-Mississippi West, the debate over the admission of new states loomed. In Utah, Mormons were also making claims to an independent state they called Deseret. By 1850, California wanted admission as a free state. With so many competing dynamics underway, and with Zachary Taylor dead and replaced by his Vice President, Whig Millard Fillmore, the 1850s were off to a troubling start.