Manifest Destiny and Slavery

Updated on January 6, 2013


As a result of the annexation of Texas and the Mexican-American war the United States gained a large swath of land, what is now the southwest. The Mexican army was soundly defeated by the American forces and their victory was greatly celebrated. However, almost immediately after the war heated debate began on whether or not to extend slavery into these newly acquired territories. These territories had the potential to upset the careful balance between slave states and free states. The country was fractured along both partisan and sectional lines. The resulting compromise of 1850 only managed to delay the crises for another decade. The American acquisition of the southwest not only re-ignited the debate on slavery; it made conflict over it almost inevitable.

The national debate over the extension of slavery westward had been largely tabled by the Missouri Compromise in 1820, which prohibited slavery north of the 36-30 line. Politicians on the national stage were eager to prevent a debate over slavery because both political parties, the Democrats and the Whigs, depended on support from both the north and the south in order to win the presidency and congress. Presidential candidates would often either remain on the fence of avoid the issue all together. After 1820 the issue was pushed to the sidelines until further westward expansion re-ignited the debate.

In 1836 Texas had managed to win its independence from Mexico. Later that year they petitioned the US for statehood. Texas was a slave state and many northerners were concerned that annexation would upset the balance between the slave states and the free states. Additionally, Mexico had never recognized Texan independence and may declare war should the United States annex them. As a result, the measure failed to pass the senate.

However, several years later rumors of a possible attempt at re-conquest by Mexico cause Texas to again petition for statehood. This time not only was there the possibility of a Mexico taking back Texas, something which most Americans would have opposed, there were rumors that Great Britain was going to intervene on the Texans behalf. Allegedly the British were prepared to safeguard Texas’s independence from Mexico if in return Texas would abolish slavery. The British Prime Minister denied this claim but nevertheless it infuriated not just the south because of abolition but the North as well due to their fears of British imperialism. Eventually Texas was annexed as a salve state, which of course strengthened the pro-slavery position by adding new congressmen and more Southern electoral votes.

A Divisive Peace

One year after the annexation of Texas, the United States found itself in a war with Mexico over a territorial dispute concerning the border between two nations. The war was one of the most unpopular in American history. Both the Whigs and anti-slavery Democrats opposed the conflict. The military victories during the war glossed over the controversy for a brief time. However, when the war was won, partisanship and sectarianism divided the country.

There was a major debate over what terms the United States should impose on Mexico. Some, the “All Mexico” movement, wanted total annexation. While others, the “No Territory” movement, wanted to annex nothing. In the end, the treaty of Guadalupe-Hidalgo ceded Arizona, New Mexico, California, Utah, and Nevada. Almost immediately debate began over whether or not slavery would be permitted in the newly acquired territories.

The expansion of slavery was critical to both sides because the new territories had the potential to offset the existing balance between the slave and free states. About half the country was free and the other half slave. If the free states gain a majority it could threaten the future of slavery in the South. Likewise, if slavery were expanded westward it would give the slave holders dominance in the country and prevent any future attempt at abolition. The South was already threatening secession over the issue.

Slavery Dominates The Election

The expansion of slavery became the most important issue in the 1848 presidential election. The Whigs nominated war hero Zachary Taylor, a southern slaveholder. At the Democrats convention they nominated Lewis Cass, who although a northerner was suspected of being pro-slavery. This combined with the fact that the adopted platform was silent on the issue of slavery and its expansion resulted in the anti-slavery Democrats walking out of the convention.

They staged a convention of their own in New York and with several abolitionists and anti-Taylor Whigs formed the Free Soil Party. Former President Martin van Buren was nominated as their candidate. The party took a staunch stance against extending slavery westward. They only finished with 10 percent of the popular vote; however they did manage to come in second in New York, where anti-slavery sentiments were the strongest. They did however; manage to elect several members to congress and expose, and perhaps deepen the cracks in the political system over slavery.

Taylor was victorious but his party lacked control over congress. There was no outright majority in the House of Representatives, and it was the Democrats that held the most seats. 12 Free Soilers and 1 anti-immigration nativist prevented either party from having control. After dozens of failed ballots to select a speaker the House finally agreed to accept a plurality rather than a majority to choose one. In doing so they managed to select a Democratic speaker but the political divisions only deepened.

The Compromise

The issue of what to do with the western territories was far more complex than simply whether or not they would be slave or free. Texas had a territorial dispute with New Mexico. The South sided with Texas as it was already a slave state. The North opposed them fearing further expansion of slavery. Furthermore, Texas had a great deal of debt leftover from their days as a republic that they were struggling to pay off. Complicating things further was Utah, which had been settled by the Mormons after they were driven out of Illinois where their founder was murdered. Their new leader, Brigham Young, wanted the admission of the state of Deseret, a Mormon state that would have included all of present day Utah and Nevada as well as most of Arizona. Additionally, the discovery of gold brought tens of thousands of immigrants to California. A vast majority of these settlers were from the free states and as a result, any constitution they drafted would likely outlaw slavery.

James Polk, before he left office proposed extending the Missouri Compromise westward to include the newly acquired lands but it was dead on arrival at congress. President Taylor, his successor, was eager to solve the issue of the western territories before it could tear the nation apart. He saw himself as a Washingtonesque figure who could mediate the two sides of the issue. He proposed admitting both California and New Mexico as free states. Once New Mexico was admitted its dispute with Texas could be settled by the courts. This was met with a great deal of opposition on congress. Senator Stephen Douglas of Illinois proposed the idea of “popular sovereignty” a potential compromise whereby the territories choose for themselves whether to be slave or free. As the debate raged on sectarian divisions grew deeper. The Southerners held a convention in Nashville to consider secession if slavery was not extended westward.

A deal was eventually brokered, which came to be known as the Compromise of 1850, by Henry Clay, Douglas, and several other congressmen. The terms were; California was admitted as a free state, New Mexico and Utah were set up as territories and to decide the slavery issue for themselves, both territories ended up permitting it. Also, Texas abandoned its claims on New Mexico in exchange for federal assumption of Texas’ state debt. The slave trade in DC was outlawed but slavery was still permitted, and fugitive slave laws were strengthened. Taylor opposed the compromise but his untimely death led to Millard Fillmore’s ascension to the Presidency. Fillmore was in favor of the proposal and signed it into law. The compromise failed to end the debate over slavery in America. It only delayed the conflict for another decade.

The annexation of Texas and the territorial gains from the Mexican-American war threatened to upset the balance of power between the slave states and the free states. Tensions over the issue reached a new high and the country became polarized as never before. A conflict over the issue became almost inevitable. The eventual settlement in 1850 only delayed the problem for another 10 years.

Questions & Answers


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        Kierstan Bailey 

        7 months ago

        Hey Kierstan Bailey, were you able to finish your Texas History assignment from two years ago

      • profile image

        kierstan bailey 

        2 years ago

        i need an answer and i dont want to read because i have to do thus paaper for tx history. Can you proposea solution that would have appeased both sides of this debate

      • profile image


        3 years ago



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