Imagine you’re part of a growing nation in the early 1800s. Different parts of the country have fundamentally different laws about slavery, and as new territories open up west, a critical question emerges: what’s the standard going forward?

In 1820, the nation aligns on a compromise. The Missouri Compromise draws a literal line across the map at 36°30’ latitude, establishing that slavery cannot expand north of this line in future territories, but can exist south of it. It’s not a solution to slavery itself, but it creates a rule everyone can follow. For over three decades, this framework holds.

Then a slave named Dred Scott gets into the mix. Scott had spent substantial time in free states and territories where slavery was banned. When he sued for his freedom, he argued that living on free soil should make him free—exactly what the Missouri Compromise seemed to promise.

But in 1857, the Supreme Court delivered a devastating blow. They ruled that the Missouri Compromise was unconstitutional—Congress had no power to restrict slavery in territories. Even worse, they declared that Black people, whether enslaved or free, could never be U.S. citizens. The carefully constructed compromise was destroyed.

The Civil War breaks out just a few years later. Only after that devastating conflict does the nation finally establish clear principles: the 13th Amendment (1865) declares that “Neither slavery nor involuntary servitude, except as a punishment for crime whereof the party shall have been duly convicted, shall exist within the United States.” Lincoln was supportive of this amendment and championed it through Congress, but was assassinated before it was ratified. The 14th Amendment (1868) establishes that “All persons born or naturalized in the United States, and subject to the jurisdiction thereof, are citizens of the United States” and guarantees that no state shall “deny to any person within its jurisdiction the equal protection of the laws”—directly overturning everything Dred Scott stood for.