Why did the expansion of slavery become the most divisive political issues in the 1840s and 1850s?

By the beginning of the 19th century, slavery in the U.S. was firmly established with a series of statutes and penal codes enacted in various states to regulate the activity of slaves and all conduct involving slaves and free blacks. With the Louisiana Purchase, the question of slavery became both geographical and political, and ushered in a period of national debate between pro- and anti-slavery states to gain political and economic advantage. But by 1820, Congress was embroiled in the debate over how to divide the newly acquired territories into slave and free states.

The Missouri Compromise—also referred to as the Compromise of 1820—was an agreement between the pro- and anti-slavery factions regulating slavery in the western territories. It prohibited slavery in new states north of the border of the Arkansas territory, excluding Missouri. Constitutionally, the Compromise of 1820 established a precedent for the exclusion of slavery from public territory acquired after the Constitution, and also recognized that Congress had no right to impose upon states seeking admission to the Union conditions that did not apply to those states already in the Union. After Missouri's admission to the Union in 1821, no other states were admitted until 1836 when Arkansas became a slave state, followed by Michigan in 1837 as a free state. Indeed, the debate over slave and free states remained relatively calm for almost 30 years. However by the late 1840s, several events occurred that upset the balance: the U.S. added new territory as a result of the Mexican war, and the question of whether that territory would be slave or free arose again. California, beneficiary of an increased population because of the gold rush—petitioned Congress to enter the Union as a free state. At the same time, Texas laid claim to territory extending all the way to Santa Fe. Of course Washington, D.C., the nation’s capital, not only allowed slavery but was home to the largest slave market in North America.

In January 1850, Henry Clay presented a bill that would become known as the Compromise of 1850. The terms of the bill included a provision that Texas relinquish its disputed land in exchange for $10 million to be paid to Mexico. The territories of New Mexico, Nevada, Arizona, and Utah were defined while leaving the question of slavery off the table, on the understanding that the issue would be decided when the territories applied for statehood. In addition, the slave trade would be abolished in the District of Columbia, although slavery would still be permitted in the nation’s capitol. It was agreed that California would be admitted as a free state, but the Fugitive Slave Act was passed to mollify pro-slavery states. This bill was the most controversial of all the bills that made up the Compromise of 1850. According to its tenets, citizens were required to aid in the recovery of fugitive slaves. Fugitives had no right to a jury trial. The cases were handled by special commissioners, who were paid $5 if a fugitive was released and $10 if the captive was returned to slavery. In addition, the act called for changes that made the process for filing a claim against a fugitive easier for slave owners. The new law was devastating. Many former slaves who had been attempting to build lives in the North left their homes and fled to Canada, which added approximately 20,000 blacks to its population over the following decade. Harriet Jacobs, a fugitive living in New York, described this period as “the beginning of a reign of terror to the colored population.” She was one of the runaways who remained in New York, despite learning that slave catchers had been hired to track her down. Many were captured and returned to slavery, however, including Anthony Burns, a fugitive living in Boston. Even free blacks, too, were captured and sent to the South, completely defenseless with no legal rights. The compromise lasted until the passage of the Kansas-Nebraska Act in 1854, when Illinois Senator Stephen Douglas proposed legislation allowing the issue of slavery to be decided in the new territories.

In 1801, Congress extended Virginia and Maryland slavery laws to the District of Columbia, establishing a federally sanctioned slave code.

In 1803, the Louisiana Purchase added Creoles and French settlers to the U.S. population. Congress approved the Louisiana Purchase from France for $15 million, which virtually doubled the country’s land size. It also re-ignited controversy over the spread of slavery in the territory.

In 1807, Congress banned the importation of slaves into the U.S., although smuggling continued in some parts of the South. Once the transatlantic slave trade was prohibited, domestic slave trading throughout the South increased.

The 1820 census added free colored persons to its racial categories.

In 1820, the Missouri Compromise brought Missouri and Maine into the Union. By this time more than 20,000 Indians lived in virtual slavery on California missions. The same year, Congress made trade in foreign slaves an act of piracy.

In 1821, Missouri entered the Union as the 24th state and a slave-holding state, maintaining the balance of slave and free states.

The Office of Indian Affairs was created in 1824.

In 1825, a ship operated by the U.S. Revenue seized a slave ship, the Antelope, sailing under a Venezuelan flag with a cargo of 281 Africans. The case was brought before the U.S. Supreme Court, which issued a unanimous opinion declaring the slave trade to be a violation of natural law. Only some of the Africans were set free, however, since the ruling also held that the U.S. could not prescribe law for other nations, and the slave trade was legal in Spain, Portugal and Venezuela. The 39 Africans designated by the court as property of Spain and the Antelope itself were restored to their owners.

The Compromise of 1850 admitted California as a free state; voters in New Mexico and Utah territories would decide whether they would be slave or free upon applying for statehood.

The new Fugitive Slave Act, also passed in 1850, made the federal government responsible for apprehending fugitive slaves in the North, and sending them back to the South. This extended slavery and its enforcement beyond the South. The South, however, felt that even this law was not strong enough, and the demand for more effective legislation resulted in enactment of a second Fugitive Slave Act that same year. However, the law was so severe that its implementation was open to abuses that defeated its purpose. Even during the Civil War, the Fugitive Slave Acts were used to prosecute blacks fleeing their masters in border states that were loyal to the Union. The acts were eventually repealed, but not until June of 1864.

In 1851 Shadrach Minkins, an African American working as a waiter in Boston, was abducted by slave catchers. Before he could be freed by legal means in a challenge to the Fugitive Slave law, Minkins was rescued by a group of African Americans.

In 1854, the Kansas-Nebraska Act passed, dividing the region along the 40th parallel, with Kansas to the south and Nebraska to the north, and providing both territories the right to vote on whether to be slave or free. For all practical purposes the act effectively repealed the Missouri Compromise and the Compromise of 1850, which had attempted to regulate the spread of slavery. As a result of the new law, both pro- and anti-slavery supporters tried to convince settlers to move to Kansas in order to sway the vote. The New England Emigrant Aid Company, an anti-slavery group, was very successful, and a group of anti-slavery activists was established around the town of Lawrence, Kansas. At the same time, pro-slavery settlers from Missouri began moving across the border to Kansas, some establishing themselves as residents of the territory, others simply coming across to vote. They were called “border ruffians” by their opponents. Lecompton, Kansas, the territorial capital, boiled with tension over the issue, and so-called “free-soilers” felt so threatened there that they set up their own unofficial legislature at Topeka. The enmity between the sides verged on civil war, and the period became known as "Bleeding Kansas."

The Dred Scott decision was handed down in 1857, which denied citizenship to free and enslaved blacks.

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To many nineteenth-century Americans, the expansion of slavery into western territories caused a great deal of controversy. Since the drafting of the Constitution in 1787, the North and the South had grown further apart in terms of economy, ideology, and society. The North, especially, was afraid that the South would force its “peculiar institution” upon the entire Union. These fears were realized when the expansion of slavery into western territories entered Congressional debates. The federal government, hoping to prevent a civil war, temporarily resolved the issue with compromises. As the compromises appeared to become more one-sided, however, sectional divides between the North and South became more pronounced.

  • Watch Edward L. Ayers on the Civil War from The Gilder Lehrman Institute

The Sectional Divide between the North and the South

While the South utilized slavery to sustain its culture and grow cotton on plantations, the North prospered during the Industrial Revolution. Northern cities, the center of industry in the United States, became major metropolises due to an influx of immigrants. With this willing and cheap workforce, the North did not require a slave system. Although some northerners found the institution of slavery morally reprehensible, most did not believe in complete racial equality either. Slavery became even more divisive when it threatened to expand westward because non-slaveholding white settlers did not want to compete with slaveholders in the new territories.

Why did the expansion of slavery become the most divisive political issues in the 1840s and 1850s?
Cowan’s Auctions, 1863.A printed broadside recruiting men of color to enlist in the U.S. military after the Emancipation Proclamation in 1863. The broadside was written by Frederick Douglass, signed by Douglass along with 54 leaders in the Philadelphia African American community, and published in Philadelphia, Pennsylvania.

First Steps Towards Controlling Slavery and Westward Expansion

Politicians were forced to deal with the issue of slavery and its westward expansion as early as the Missouri Compromise of 1820. The States had previously maintained a shaky balance in the Senate with an equal number of representatives from both Slave and Free States. As Missouri prepared to enter the Union as a Slave State, this tentative balance threatened to come undone. Henry Clay of Kentucky temporarily solved the issue by crafting the Missouri Compromise, bringing Missouri into the Union as a Slave State and, as a balance, Maine entered as a Free State. The Compromise also made future bondage illegal in all areas of the Louisiana Purchase north of the 36°30′ parallel with the exception of Missouri; all future states below this line would become Slave States.  This Compromise solved the immediate problem of slavery in the Louisiana Purchase by sweeping the real issue of slavery under the rug in order to placate both northern and southern politicians. In the years to come, politicians of both northern and southern states would not be so quick so compromise.

Conquests from Mexico

When the United States entered into a war with Mexico over Texas and its western territories, the issue of extending slavery in the west resurfaced in Congress. Representative David Wilmot of Pennsylvania first introduced a potential solution to the problem in 1846. His proposed amendment stated:

“…the acquisition of any territory from the Republic of Mexico by the United States, by virtue of any treaty which may be negotiated between them, and to the use by the Executive of the moneys herein appropriated, neither slavery nor involuntary servitude shall ever exist in any part of said territory, except for crime, whereof the party shall first be duly convicted.”

Why did the expansion of slavery become the most divisive political issues in the 1840s and 1850s?
Daguerreotype of the Virginia regiment and Webster’s battalion in Saltillo, Mexico, during the Mexican-American War.

Wilmot’s proviso suggested that slavery should be prohibited in any territories acquired from Mexico. This would encourage white farmers to move west and implied that slavery was not an institution that should stretch far beyond its borders. Fearful of the southern “Slave Power” in Congress, many northern politicians quickly backed Wilmot’s amendment. Meanwhile, southern politicians railed that such an act was unconstitutional and vehemently blocked the passage of the Wilmot Proviso.  As a result, it never passed and the issue of slavery in westward territories remained a topic of heated debate.

Territories Becoming States

Congress was forced to revisit this issue yet again when California petitioned for statehood in 1849. Because California appeared to have anti-slavery inclinations, southern democrats were reluctant to let it enter the Union and disrupt the sectional balance in Congress. The resulting Compromise of 1850 was supposed to ensure that the interests of both sides remained intact. For the North, the Compromise guaranteed that California would enter the Union as a Free State and the slave trade would end in the District of Columbia. For the South, the Compromise promised that popular sovereignty would decide the question of slavery in the Utah and New Mexico territories. Furthermore, the Compromise reshaped the existing Fugitive Slave Act and required northerners to help capture runaway slaves.  This Act enraged the people of the North as it was a direct violation of their state laws and many argued that the “people of the free states are made [plantation owners’] constables and slave-catchers, bound as ‘good citizens’ to engage in a business at which their humanity must revolt…”

Kansas-Nebraska Act

Just four years later in 1854, new statehood controversies arose and forced the issue of slavery back into Congress. Kansas and Nebraska were both large territories petitioning for statehood. However, southerners opposed their admittance because the Missouri Compromise mandated that these two territories would enter as Free states. To satisfy southern states already threatening session, Congress passed the Kansas-Nebraska Act.  This new act repealed the Missouri Compromise; instead, the people living in Kansas and Nebraska would vote to determine the fate of the states.  When voters from nearby Missouri snuck into Kansas in order to vote to make the territory a slave state, tensions between the two sides exploded. War broke out in Kansas between pro-slavery sympathizers and abolitionists, earning it the nickname “bleeding Kansas.”  The violence in the west would soon spread east.

Check out this clip which highlights the escalating violence between the north and south on the issue of westward expansion:

The Beginnings of the Civil War

The fighting in Kansas foreshadowed the great fighting that would take place just six years later. The compromises of the early nineteenth century did not settle the issue of slavery and westward expansion. Instead, they suppressed the issue and acted as temporary salves. However, as the compromises appeared to benefit Slave States more often than they did Free States, sectional antagonisms between the North and the South were becoming more distinct. Ultimately, negotiations unraveled and a bloody Civil War erupted.

This article helps answer “What role did western expansion play in the Civil War?” Themes: causes of the Civil War, the Civil War and Western Expansion, slavery, slavery and western expansion, Wilmot’s Proviso, Antebellum America, Bleeding Kansas, Civil War, Western Expansion, The West, the American West, African American history, economic history