In five minutes: from the Missouri Compromise to Dred Scott
The Missouri Compromise of 1820 was the first big deal that tried to settle whether slavery could spread into the new western lands. It worked for about three decades, mostly by keeping the number of free and slave states equal and by drawing one line across the map. Then new territory, new laws and a Supreme Court ruling wore it away. By 1857 the compromise was dead, and the fight it had delayed was out in the open.
This page follows that unraveling in four steps. It is part of our hub on 19th-century America, and it sets up the story told in the American Civil War.
Background: why Missouri mattered in 1819
In 1819 the Union had 22 states: 11 free and 11 slave. That balance mattered because every state sends two senators. The North had more people and more seats in the House of Representatives, so the Senate was the one place where the South could block laws it feared.
Then Missouri, a part of the Louisiana Purchase where thousands of enslaved people already lived, asked to join as a slave state. In February 1819, Representative James Tallmadge of New York proposed two conditions: no more enslaved people could be brought into Missouri, and children born there to enslaved parents would be freed at age 25. The House, with its northern majority, passed the idea. The Senate rejected it. Congress was stuck for the best part of a year.
The Missouri Compromise of 1820
The deadlock was broken by a package deal, steered by Henry Clay, the Speaker of the House. It had three parts:
- Missouri would enter the Union as a slave state.
- Maine, which separated from Massachusetts, would enter as a free state, keeping the count even at 12 to 12.
- In the rest of the Louisiana Purchase north of latitude 36°30′, the line of Missouri's southern border, slavery would be banned. South of the line it stayed legal.
The 36°30′ line came from an amendment by Senator Jesse Thomas of Illinois. President James Monroe signed the law on March 6, 1820. Maine became a state on March 15, 1820. Missouri waited until August 10, 1821, because its state constitution tried to restrict free Black people from entering the state, which set off a second argument in Congress.
The compromise did not say slavery was right or wrong. It only said where it could go. Thomas Jefferson, then retired in Virginia, wrote that the crisis struck him like “a fire bell in the night” and warned that it might threaten the Union. At the time, most of the land north of the line had almost no American settlers, so the real test of the deal lay in the future.
Why it broke: the Mexican War and the Compromise of 1850
The test came with the Mexican–American War (1846–1848). In 1846 Representative David Wilmot of Pennsylvania proposed that slavery be banned from any land won from Mexico. The House passed the Wilmot Proviso more than once, but the Senate never did. The idea still turned a quiet question into the main issue in national politics.
In the Treaty of Guadalupe Hidalgo (1848), the United States gained a huge area that included California, Utah and New Mexico. The 36°30′ line had been written only for the Louisiana Purchase, so it did not clearly apply. Then the Gold Rush of 1849 filled California with settlers, and California asked to join as a free state, which would upset the balance in the Senate.
The answer was the Compromise of 1850, a set of separate laws:
- California entered as a free state.
- Utah and New Mexico became territories where settlers would decide on slavery themselves. This idea is called popular sovereignty.
- Texas gave up its claims to part of New Mexico and received $10 million from the federal government.
- The slave trade, but not slavery itself, was banned in Washington, D.C.
- A much stronger Fugitive Slave Act required officials, and even ordinary citizens, to help capture people who had escaped slavery. Those accused were denied a jury trial.
Henry Clay proposed the package, and Senator Stephen Douglas of Illinois finally got it passed by splitting it into separate bills. President Zachary Taylor died in July 1850, and Millard Fillmore signed the laws that September. Many Americans hoped the issue was finished. But the Fugitive Slave Act angered people in the North who had never thought of themselves as abolitionists, and Harriet Beecher Stowe’s novel Uncle Tom’s Cabin (1852) turned that anger into a bestseller.
The Kansas-Nebraska Act (1854)
In 1854 Stephen Douglas wanted to organize the land west of Missouri and Iowa so that a railroad could run west from Chicago. To win Southern votes, his bill created two territories, Kansas and Nebraska, let settlers decide on slavery by popular sovereignty, and declared the 36°30′ restriction of 1820 “inoperative.” In practice, it repealed the Missouri Compromise. President Franklin Pierce signed it on May 30, 1854.
The reaction in the North was fierce. The Whig Party fell apart, and anti-slavery politicians formed the Republican Party in 1854. Abraham Lincoln, who had left politics for several years, returned to public life in 1854 to speak against the act.
Kansas then became a battleground. Pro-slavery settlers, many of them crossing over from Missouri, and anti-slavery settlers from the North rushed in, and each side set up its own government. In May 1856, pro-slavery men attacked the free-state town of Lawrence. Days later, John Brown and his followers killed five pro-slavery settlers at Pottawatomie Creek. In the same week, Representative Preston Brooks of South Carolina beat Senator Charles Sumner with a cane on the Senate floor after a speech about Kansas. People began calling the violence “Bleeding Kansas.”
Dred Scott v. Sandford (1857)
The last step came from the courts. Dred Scott was an enslaved man whose owner, an army surgeon named John Emerson, had taken him to Illinois and to Wisconsin Territory, both places where slavery was banned. After years there, Scott returned to Missouri, and in 1846 he sued for his freedom in a St. Louis court, arguing that living on free soil had made him free. The case reached the U.S. Supreme Court as Dred Scott v. Sandford (the court record misspells the owner’s name, Sanford).
On March 6, 1857, Chief Justice Roger Taney announced the decision, 7 to 2. The Court ruled that:
- people of African descent, whether enslaved or free, could not be U.S. citizens and had no right to sue in federal court;
- Congress had no power to ban slavery in the territories, so the Missouri Compromise had been unconstitutional all along.
Justices Benjamin Curtis and John McLean dissented. The ruling meant that the central Republican goal, keeping slavery out of the territories, was now illegal in the Court’s view. Many Northerners concluded that the judiciary was serving the slave power. In 1858 Lincoln warned that “a house divided against itself cannot stand” and ran against Douglas for the Senate. Scott himself was freed by a new owner soon after the ruling and died in 1858. The Thirteenth Amendment (1865) ended slavery, and the Fourteenth Amendment (1868) made everyone born in the United States a citizen, which overturned the Dred Scott holding.
What exams ask
- Define: Missouri Compromise, 36°30′, popular sovereignty, Fugitive Slave Act, Bleeding Kansas, Dred Scott v. Sandford.
- Compare the two compromises: 1820 drew a line; 1850 used popular sovereignty and a stronger Fugitive Slave Act.
- Cause and effect: the Mexican Cession created the 1850 crisis; the Kansas-Nebraska Act repealed the 1820 line and produced the Republican Party.
- Significance (AP style): each deal postponed the conflict but also hardened sectional identities, because the North and South came to see compromise as a trap.
- Timeline questions: 1820, 1850, 1854 and 1857 are the four dates to know.
Read next
- 19th-Century America: Expansion, Civil War and the Gilded Age: the hub for the whole century, so you can see where this story fits.
- Who Was Abraham Lincoln?: how the Kansas-Nebraska Act and Dred Scott pulled him back into politics.
- The American Civil War (1861–1865): what happened after compromise failed.
