From before the United States declared independence in 1776, slavery had been a contentious issue. The Founding Fathers, in drafting the Constitution had conspicuously ignored the issue. But, as the 1800s progressed, it was a political problem that could not be avoided. Since more people lived in the northern, free states they would always have a majority of representatives in the House. But the Senate was different. Every state sends two Senators to Washington, and there the question of slavery would be decided. If either the free states of the North, or the slave holding states of the South were able to take a majority, their view of America’s future would prevail.

Most white Americans agreed that western expansion was crucial to the health of the nation. But what should be done about slavery in the West? As the United States gained new territory, especially after defeating Mexico in the 1840s, the fight about the expansion of slavery became a major question that spawned political feuds, actual fighting, and gave birth to new political parties.

Slavery might have divided the nation, but slavery had been dividing the nation for generations. Perhaps it was something more that brought all of that animosity to the level of war in 1860.

What do you think? Did westward expansion cause the Civil War?


The contradictions inherent in the expansion of white male voting rights can also be seen in problems raised by western migration. The new western states were at the forefront of more inclusive voting rights for white men, but their development simultaneously devastated the rights of Native American communities. Native American rights rarely became a controversial public issue. This was not the case for slavery, however, as Northern and Southern whites differed sharply about its proper role in the West.

The incorporation of new western territories into the United States made slavery an explicit concern of national politics. Balancing the interests of slave and free states had played a role from the very start of designing the federal government at the Constitutional Convention in 1787. The crucial compromise there that sacrificed the rights of African Americans in favor of a stronger union among the states exploded once more in 1819 when Missouri petitioned to join the United States as a slave state.

In 1819, the nation contained eleven free and eleven slave states creating a balance in the U.S. senate. Missouri’s entrance threatened to throw this parity in favor of slave interests. The debate in Congress over the admission of Missouri was extraordinarily bitter after Congressman James Tallmadge from New York proposed that slavery be prohibited in the new state.

The debate was especially sticky because defenders of slavery relied on a central principle of fairness. How could the Congress deny a new state the right to decide for itself whether or not to allow slavery? If Congress controlled the decision, then the new states would have fewer rights than the original ones.

Henry Clay, a leading congressman, played a crucial role in brokering a two-part solution known as the Missouri Compromise. First, Missouri would be admitted to the union as a slave state, but would be balanced by the admission of Maine, a free state, that had long wanted to be separated from Massachusetts. Second, slavery was to be excluded from all new states in the Louisiana Purchase north of the southern boundary of Missouri. People on both sides of the controversy saw the compromise as deeply flawed. Nevertheless, it lasted for over thirty years until the Kansas-Nebraska Act of 1854 determined that new states north of the boundary deserved to be able to exercise their sovereignty in favor of slavery if they so choose.

Democracy and self-determination could clearly be mobilized to extend an unjust institution that contradicted a fundamental American commitment to equality. The Missouri crisis probed an enormously problematic area of American politics that would explode in a civil war. As Thomas Jefferson observed about the Missouri crisis, “This momentous question, like a fire-bell in the night, awakened and filled me with terror.”


While the admission of Missouri as a state had posed a serious political challenge, the Mexican-American War of 1846 to 1848 created the most problems of all. After Mexico surrendered and ceded half of its territory to the United States, there were vast new tracts of land, mostly in the southern half of the West, which were in question. Would slavery be allowed in these new territories?

Abolitionists rightly feared that attempts would be made to plant cotton in the new territory, which would bring the blight of slavery. Slaveholders feared that if slavery were prohibited in the new territory, southern slaveholding states would lose power in Congress.

Even before the Treaty of Guadalupe Hidalgo ending the war had been ratified by the Senate, both houses of Congress became the scene of angry debate over the spoils of war. Congress represented every political philosophy regarding slavery. Legal scholars discussed the right of Congress — or anyone else — to restrict slavery from the new lands. The specter of secession had risen again. Desperately the elder statesmen of the federal legislature proposed methods of keeping the country together.

The country’s founders left no clear solution to the issue of slavery in the Constitution. Popular sovereignty, amendment, nullification, and secession were all discussed as possible remedies. In the end, conflict was avoided with the passing of the Compromise of 1850.

By the standards of his day, David Wilmot could be considered a racist. Yet the Pennsylvania representative was so adamantly against the extension of slavery to lands ceded by Mexico, he made a proposition that would divide the Congress. On August 8, 1846, Wilmot introduced legislation in the House that boldly declared, “neither slavery nor involuntary servitude shall ever exist” in lands won in the Mexican-American War. His proposal has become known as the Wilmot Proviso. If he was not opposed to slavery, why would Wilmot propose such an action? Why would the North, which only contained a small, but growing minority, of abolitionists, agree?

Wilmot and other Northerners were angered by President Polk. They felt that the entire Cabinet and national agenda were dominated by Southern minds and Southern principles. Polk was willing to fight for Southern territory, but proved willing to compromise when it came to the North. Polk had lowered the tariff and denied funds for internal improvements, both to the dismay of Northerners. Now they felt a war was being fought to extend the Southern way of life. The term Slave Power jumped off the lips of northern lawmakers when they angrily referred to their Southern colleagues. It was time for Northerners to be heard.

Though Wilmot’s heart did not bleed for the slave, he envisioned California as a place where free white Pennsylvanians could work without the competition of slave labor. Since the North was more populous and had more Representatives in the House, the Wilmot Proviso passed. Laws require the approval of both houses of Congress, however. The Senate, equally divided between free states and slave states could not muster the majority necessary for approval. Angrily the House passed the Wilmot Proviso several times, all to no avail. It would never become law.

For years, the arguments for and against slavery were debated in the churches and in the newspapers. The House of Representatives had passed a gag rule forbidding the discussion of slavery for much of the previous decade. The issue could no longer be avoided. Lawmakers in the House and Senate, North and South, would have to stand up and be counted.


Henry Clay of Kentucky, John C. Calhoun of South Carolina, and Daniel Webster of Massachusetts dominated national politics from the end of the War of 1812 until their deaths in the early 1850s. Although none would ever be President, the collective impact they created in Congress was far greater than any President of the era, with the exception of Andrew Jackson. There was one issue that loomed over the nation throughout their time in power — slavery. They were continuously successful in keeping peace in America by forging a series of compromises. The next generation’s leaders were not.

The Gold Rush led to the rapid settlement of California which resulted in its imminent admission as the 31st state. Southerners recognized that there were few slaves in California because Mexico had prohibited slavery. Immediate admission would surely mean California would be the 16th free state, giving the non-slave-holding states an edge in the Senate. Already holding the House of Representatives, the free states could then dominate legislation.

Texas was claiming land that was part of New Mexico. As a slave state, any expansion of the boundaries of Texas would be opening new land to slavery. Northerners were opposed. The North was also appalled at the ongoing practice of slavery in Washington, DC, the nation’s capital — a practice the South was not willing to let go. The lines were drawn as the three Senatorial giants took the stage for the last critical time.

Secondary Source: Illustration

A page from a history book for children published in 1917 celebrating the great statesmen of the mid-1800s.

Henry Clay had brokered compromises before. When the Congress was divided in 1820 over the issue of slavery in the Louisiana Territory, Clay set forth the Missouri Compromise. When South Carolina nullified the tariff in 1832, Clay saved the day with the Compromise Tariff of 1833. After 30 years in Congress and three unsuccessful attempts at the Presidency, Clay wanted badly to make good with yet another nation-saving deal. He put forth a set of eight proposals that he hoped would pass muster with his colleagues.

John C. Calhoun took to the floor next. Although sick and dying with consumption, he sat sternly in the Senate chamber, as his speech was read. The compromises would betray the South, he claimed. Northerners would have to agree to federal protection of slavery for the South to feel comfortable remaining in the Union. His words foreshadowed the very doom to the Union that would come within the decade.

Daniel Webster spoke three days after Calhoun’s speech. With the nation’s fate in the balance, he pleaded with Northerners to accept Southern demands, for the sake of Union. Withdrawing his former support for the Wilmot Proviso, he hoped to persuade enough of his colleagues to move closer to Clay’s proposals. Although there was no immediate deal, his words “liberty and union, now and forever, one and inseparable” echoed in the minds of the Congressmen as they debated into that hot summer.


In the heat of the Wilmot Proviso debate, many Southern lawmakers began to question the right of Congress to determine the status of slavery in any territory. According to John Calhoun, the territories belonged to all the states. Why should a citizen of one state be denied the right to take his property, including slaves, into territory owned by all? This line of reasoning began to dominate the Southern argument. The Congress had a precedent for outlawing slavery in territories. It had done so in the Old Northwest with the passing of the Northwest Ordinance in 1787. The Missouri Compromise also had banned slavery above the 36º30′ latitude line. But times were different.

As the Mexican War drew to a close and no compromise could be reached in the Wilmot argument, the campaign for President became heated. The Democratic standard bearer, Lewis Cass of Michigan, coined the term popular sovereignty for a new solution that had begun to emerge. The premise was simple. Let the people of the territories themselves decide whether slavery would be permitted. The solution seemed perfect. In a country that has championed democracy, letting the people decide seemed right, if not obvious.

However simple popular sovereignty seemed, it was difficult to put into practice. By what means would the people decide? Directly or indirectly? If a popular vote were scheduled, what guarantees could be made against voter fraud? If slavery were voted down, would the individuals who already owned slaves be allowed to keep them? Cass and the Democrats did not say. His opponent, Zachary Taylor, ignored the issue of slavery altogether in his campaign, and won the election of 1848.

As the 1840s melted into the 1850s, Stephen Douglas became the loudest proponent of popular sovereignty. As long as the issue was discussed theoretically, he had many supporters. In fact, to many, popular sovereignty was the perfect means to avoid the problem. But problems do not tend to disappear when they are evaded — they often become worse.


With the issue of slavery in the territories threatening to divide the nation yet again, the giants — Calhoun, Webster, and Clay — developed another compromise. It would be their last, great act of statesmanship. Still the Congress debated the contentious issues well into the summer. Each time Clay’s compromise was set forth for a vote, it did not receive a majority. Henry Clay himself had to leave in sickness, before the dispute could be resolved. In his place, Stephen Douglas worked tirelessly to end the fight. On July 9, President Zachary Taylor died of food poisoning. His successor, Millard Fillmore, was much more interested in compromise. The environment for a deal was set. By September, Clay’s Compromise became law.

California was admitted to the Union as the 16th free state. In exchange, the South was guaranteed that no federal restrictions on slavery would be placed on Utah or New Mexico. Texas lost its boundary claims in New Mexico, but the Congress compensated Texas with $10 million. Slavery was maintained in the nation’s capital, but the slave trade was prohibited. Finally, and most controversially, a fugitive slave law was passed, requiring Northerners to return runaway slaves to their owners under penalty of law.

The Terms of the Compromise:

For the North:
– California admitted as a free state
– Slave trade prohibited in Washington D.C.

For the South
– No slavery restrictions in Utah or New Mexico territories
– Slaveholding permitted in Washington D.C.
– Texas gets $10 million
– Fugitive Slave Act

Who won and who lost in the deal? Although each side received benefits, the North seemed to gain the most. The balance of the Senate was now with the free states, although California voted with the South on many issues in the 1850s. The major victory for the South was the Fugitive Slave Law. In the end, the North refused to enforce it. Massachusetts even called for its nullification, stealing an argument from John C. Calhoun. Northerners claimed the law was unfair. The flagrant violation of the Fugitive Slave Law set the scene for the tempest that emerged later in the decade. But for now, Americans had hope that the fragile peace would prevail.

By 1852, Clay, Calhoun, and Webster had all passed away. They left a rich legacy behind them. Clay of the West, Calhoun of the South, and Webster of the North loved and served their country greatly. The generation that followed produced no leader that could unite the country without the force of arms.


For decades, both Northern states and Southern states had threatened secession and dissolution of the Union over the question of where slavery was to be permitted. At issue was power. Both sides sought to limit the governing power of the other by maintaining a balance of membership in Congress. This meant ensuring that admission of a new state where slavery was outlawed was matched by a state permitting slavery. In the Missouri Compromise, for example, at the same time that Missouri entered the Union as a slave state, Maine entered the Union as a free state.

New states were organized into self-governing territories before they became states. Hence, they developed a position on the slavery issue well before their admission to the Union. Southerners held that slavery must be permitted in all territories. Northerners held that slavery must not be extended into new territories.

If slavery were not permitted in the territories, slavery would never gain a foothold within them and Southern power in Congress would gradually erode. If either side were successful in gaining a distinct advantage, many felt disunion and civil war would follow.

Kansas would be the battleground on which the North and South would first fight. The Kansas-Nebraska Act led both to statehood and to corruption, hatred, anger, and violence. Men from neighboring Missouri stuffed ballot boxes in Kansas to ensure that a legislature friendly to slavery would be elected. Anti-slavery, or free soil, settlers formed a legislature of their own in Topeka. Within two years, there would be armed conflict between proponents of slavery and those against it.

The Kansas-Nebraska Act of 1854 may have been the single most significant event leading to the Civil War. By the early 1850s settlers and entrepreneurs wanted to move into the area now known as Nebraska. However, until the area was organized as a territory, settlers would not move there because they could not legally hold a claim on the land. The Southern states’ representatives in Congress were in no hurry to permit a Nebraska territory because the land lay north of the 36°30′ parallel — where slavery had been outlawed by the Missouri Compromise of 1820. Just when things between the North and South were in an uneasy balance, Kansas and Nebraska opened fresh wounds.

The person behind the Kansas-Nebraska Act was Senator Stephen Douglas of Illinois. He said he wanted to see Nebraska made into a territory and, to win Southern support, proposed a Southern state inclined to support slavery. It was Kansas. Underlying it all was his desire to build a transcontinental railroad to go through Chicago. The Kansas-Nebraska Act allowed each territory to decide the issue of slavery on the basis of popular sovereignty. Kansas with slavery would violate the Missouri Compromise, which had kept the Union from falling apart for the last thirty-four years. The long-standing compromise would have to be repealed. Opposition was intense, but ultimately the bill passed in May of 1854. Territory north of the sacred 36°30′ line was now open to popular sovereignty. The North was outraged.

The political effects of Douglas’ bill were enormous. Passage of the bill irrevocably split the Whig Party, one of the two major political parties in the country at the time. Every northern Whig had opposed the bill; almost every Southern Whig voted for it. With the emotional issue of slavery involved, there was no way a common ground could be found. Most of the Southern Whigs soon were swept into the Democratic Party. Northern Whigs reorganized themselves with other non-slavery interests to become the Republican Party, the party of Abraham Lincoln. This left the Democratic Party as the sole remaining institution that crossed sectional lines. Animosity between the North and South was again on the rise. The North felt that if the Compromise of 1820 was ignored, the Compromise of 1850 could be ignored as well. Violations of the hated Fugitive Slave Law increased. Trouble was indeed back with a vengeance.


Slavery was quite likely to be outlawed in Nebraska, where cotton doesn’t grow well. The situation in Kansas was entirely different, where the land was similar to Missouri’s, which was a slave state. Kansas was to be governed by the principle of popular sovereignty. Whether Kansas was to be slave or free would be decided at the polls. Both free and slave forces were determined to hold sway.

Missouri counties that bordered Kansas were strongly pro-slavery and wanted their neighbor to be a slave state. In the fall of 1854, Senator David Atchison of Missouri led over 1,700 men from Missouri into Kansas to vote for their pro-slavery representative. These were the infamous Border Ruffians, who threatened to shoot, burn and hang those opposed to slavery.

Although their votes were later ruled fraudulent, their candidate was elected to Congress. When it came time to elect a territorial legislature the following March, almost 5,000 men came into the state from Missouri to cast illegal ballots. Pro-slavery forces had the numbers, not the ethics, on their side. Anti-slavery settlers, though the majority in Kansas, were outvoted. The result of the election through fraud was a legislature with 36 pro-slavery delegates and 3 anti-slavery delegates.

As one of their first acts, this legislature passed a harsh slave code that provided fines and imprisonment simply for expressing opinions against slavery. The death penalty would be administered to any individual found guilty of assisting slaves to revolt or escape. It also legalized the “border ruffian” vote by not requiring voters to be residents in Kansas prior to voting and made the law retroactive to the preceding elections.

Within a year, however, the population of anti-slavery residents in Kansas grew and far outnumbered legal residents of Kansas who were pro-slavery. They were not prepared to obey the laws of the Bogus Legislature, seated in Shawnee Mission. Organized under the name of Free Soilers, they drew up a free state constitution and elected a separate governor and state legislature located in Topeka. The result was a state with two governments. Violence would soon follow.

The town of Lawrence was the center of Kansas’s anti-slavery movement. It was named for Amos Lawrence, a New England financier who provided aid to anti-slavery farmers and settlers. This group went beyond simple monetary aid. New England Abolitionists shipped boxes of Sharps rifles, named Beecher’s Bibles to anti-slavery forces. The name for the rifles came from a comment by Henry Ward Beecher, the anti-slavery preacher who had remarked that a rifle might be a more powerful moral agent on the Kansas plains than a Bible. The lines were now drawn. Each side had passion, and each side had guns.

The administration of President Franklin Pierce refused to step in to resolve the election dispute resulting from the “border ruffians.” In the spring of 1856, Judge Samuel Lecompte demanded that members of the anti-slavery government in Kansas, called the Free-Soil government, be indicted for treason. Many leaders in this government lived in Lawrence. On May 21, 1856, the pro-slavery forces sprang into action. A posse of over 800 men from Kansas and Missouri rode to Lawrence to arrest members of the free state government. The citizens of Lawrence decided against resistance. However, the mob was not satisfied. They proceeded to destroy two newspaper offices as they threw the printing presses from the Free-Soil newspaper into the nearby river. They burned and looted homes and shops. As a final message to Abolitionists, they aimed their cannons at the Free State Hotel and smashed it into oblivion.

The attack inflamed almost everyone. Republicans introduced bills to bring Kansas into the Union under the free state government, while Democrats introduced bills to bring in Kansas as a slave state. Neither party alone could get the votes necessary to win. To increase readership, Republican newspapers exploited the situation in Kansas. Their attack galvanized the northern states like nothing before. It went beyond passing pro-slavery laws. The Sack of Lawrence was a direct act of violent aggression by slave-owning Southern Fire Eaters.

Secondary Source: Mural

The mural “The Tragic Prelude” immortalizes John Brown and decorates the walls of the Kansas State Capitol building. It was painted in the 1900s by John Steuart Curry.

John Brown was not a timid man. A devout reader of the Bible, he found human bondage immoral and unthinkable. The father of 20 children, he and his wife Mary settled in Kansas to wage a war on the forces of slavery. A few days after the sack of Lawrence, Brown sought revenge. He was furious that the people of Lawrence had chosen not to fight. He told his followers that they must “fight fire with fire,” and they must “strike terror in the hearts of the pro-slavery people.” In his eyes, the only just fate for those responsible for the border ruffian laws was death. A great believer in “an eye for an eye,” John Brown sought to avenge the sack of Lawrence.

Vengeance would come on the night of May 24, three days after the Lawrence affair. Setting out after dark with seven others and calling himself the Army of the North, Brown entered the pro-slavery town of Pottawatomie Creek. Armed with rifles, knives, and broadswords, Brown and his band stormed the houses of his enemies. One by one, Brown’s group dragged out helpless victims and hacked at their heads with the broadswords. In one encounter, they even killed two sons of an individual they sought. Before the night was through, five victims lay brutally slain by the hands of John Brown.

It was the South’s turn to be outraged. Destroying property was one thing, but no one had been killed at Lawrence. Brown had raised the stakes. He and his followers were doggedly hunted well into the summer. Federal troops arrested two of Brown’s sons who had not been with him. Border ruffians burned the Brown homesteads to the ground. But John Brown lived to fight another day. Now a fugitive, he traveled north where he was received by abolitionists like a cult hero. This would not be the last America would hear of John Brown. He would again make national headlines at Harper’s Ferry in 1859.

The Sack of Lawrence and the Pottawatomie Creek Massacre set off a brutal guerrilla war in Kansas. By the end of 1856, over 200 people would be gunned down in cold blood. Property damage reached millions of dollars. Federal troops were sent in to put down the fighting, but they were too few to have much effect. Kansas served as a small scale prelude to the bloody catastrophe that engulfed the entire nation just five years later.


So, slavery might have been what everyone was arguing about, but was it westward expansion that turned that argument into a war? It seems hard to imagine someone like John Brown peacefully protesting, but it’s also hard to think of a reason why Kansas would have gotten its bloody nickname if White Americans were not moving west to begin with.

What do you think? Did westward expansion cause the Civil War?



BIG IDEA: Westward expansion increased conflicts about slavery as the addition of each new state threatened to upset the balance between free and slave states in the Senate. Politicians tried compromise and popular sovereignty to deal with this problem.

Expansion of settlement greatly increased tensions that led to the Civil War because it made the question of expansion of slavery an issue politicians could not ignore.  Central to this question was the balance of power between slave states and free states in the Senate.  The House of Representatives would always be unbalanced because the North was so much more populous, but for the 40 years leading up to the war, maintaining an equal number of slave and free states was essential to keeping the nation together.

The Missouri Compromise was brokered by Henry Clay in 1820. It banned slavery in new territories north of Missouri, while admitting Missouri and Maine as slave and free states. It was the first in a series of such compromises.

After the Mexican-American War, the greatest question was whether or not to allow slavery into the Mexican Cession. The proposed Wilmot Proviso specifically banned this, but it was not adopted. The fight over the Proviso led Northerners to believe that “slave power” was taking over the federal government.

The three great senators of the early 1800s, Clay, Calhoun and Webster forged the Compromise of 1850 to keep the nation together. It preserved the Union, but in the end, it made no one happy.

The idea of popular sovereignty was proposed as a way of taking the fight over the expansion of slavery out of Congress and giving it to the people. Under this proposal, the people of each new state would vote for themselves about the question of being a slave or free state. This was put to the test with the Kansas-Nebraska Act and led to a period of violence called Bleeding Kansas, a precursor to the Civil War. John Brown and Jesse James both got their first taste of violence in Kansas.



Border Ruffians: A nickname given to a group of pro-slavery men who went to Kansas to try to terrorize the people there who were opposed to slavery.

Daniel Webster: Senator from Massachusetts. He was opposed to slavery but more than anything worked to preserve the Union and prevent Southern secession. Along with Henry Clay and John C. Calhoun he helped broker the Compromise of 1850.

Free Soil Party: A political party that existed during the 1850s. They believed that slavery should not be permitted in the territories of the West saying, “Free Men on Free Soil.” Most Free Soilers eventually joined the Republican Party.

Henry Clay: Congressman from Kentucky who ran many times but never won the presidency. He is remembered as one of the three great dealmakers of the early 1800s who helped prevent civil war over slavery by negotiating the Missouri Compromise and the Compromise of 1850.

John Brown: A fierce abolitionist who moved to Kansas with his family. He led the Pottawatomie Creek Massacre and later led an attack on the federal arsenal at Harper’s Ferry in the hope of leading a slave rebellion that would bring about the end of slavery. He was hated by Southerners but became a martyr for the abolitionist cause.

John C. Calhoun: Senator from South Carolina. In the decades before the Civil War he was the strongest voice for states’ rights and defender of slavery. Along with Henry Clay and Daniel Webster he helped broker the Compromise of 1850.

Republican Party: A political party founded in the 1850s which initially opposed the expansion of slavery into the territories of the West. Abraham Lincoln was the first Republican president. Eventually the party worked to end slavery altogether.

Stephen Douglas: Senator from Illinois. He was opposed to slavery but wanted to preserve the Union. He believed that the best way was to let the people of each new state decide for themselves if slavery would be permitted. This idea, popular sovereignty is most strongly associated with Douglas.


Popular Sovereignty: The idea that the residents of each territory should decide for themselves if they would join the Union as a free or slave state. Stephen Douglas supported this idea and it was the heart of the Kansas-Nebraska Act.

Secession: When a state or group of states leaves separates themselves from the country to form a new nation.

Slave Power: A phrase Northerners used to describe the political power Southern states had in Congress.


36th Parallel: The line of latitude that was the dividing line between the free and slave states of the west. The Missouri Compromise had banned slavery north of the line, but the Compromise of 1850 ended that ban by allowing Missouri to become a slave state. The line is the southern border of Missouri.


Bleeding Kansas: The name given to the time period of fighting between pro and anti-slavery forces in Kansas before it was admitted as a state.

Pottawatomie Creek Massacre: An attack by John Brown and his abolitionist followers on the town of Pottawatomie Creek, Kansas. They killed five people in revenge for the Sack of Lawrence. The events were part of the era known as Bleeding Kansas.

Sack of Lawrence: The town of Lawrence, Kansas was the center of the anti-slavery movement in that territory. In 1856 a group of pro-slavery men attacked and burned the town. The event was part of the era known as Bleeding Kansas.


Kansas-Nebraska Act: A law that said that when the new states of Kansas and Nebraska joined the Union, the people of those states of vote to decide if they would be slave states or free states. The law proposed by Stephen Douglass and embraced his idea of popular sovereignty as a way to avoid a political fight in Congress.

Missouri Compromise: An agreement brokered by Henry Clay in 1820 to maintain the balance of slave and free states in the Senate. Missouri entered the Union as a slave state and Maine as a free state.

Wilmot Proviso: An addition to the Treaty of Guadalupe Hidalgo that ended the Mexican American War proposed by David Wilmot. It stated that slavery would not be permitted in the new territories taken from Mexico, but was not adopted.

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