In the Fugitive Slave Act of 1793, the federal government gave local authorities in both slave and free states the power to issue warrants to "remove" any black they thought to be an escaped slave. It also made it a federal crime to help a runaway slave. The act was rarely enforced in non-slave states, but in 1850 it was strengthened with higher fines and harsher punishments. On top of that, slave hunters could legally claim that any black person they saw was an escaped slave, which not only terrorized free blacks but outraged many white people. Northerners were horrified by rumors of slave hunters luring preschool-age free black children onto boats and shipping them to the Deep South.
Before 1850, if runaway slaves were caught, they were typically killed, and sometimes tortured in a public display to scare other slaves. Punishment in the North for white people and free blacks who assisted in escapes was originally not as harsh -- typically a fine for the loss of "property" and a short jail sentence that might not be enforced. But in 1850, penalties became much steeper and included more jail time. Whites who armed slaves, which was often necessary along the dangerous route, could be executed. In the South, anyone -- white or black -- who assisted a fugitive could face death.
The state of Pennsylvania actually considered nullifying the Fugitive Slave Act (much like South Carolina would nullify part of the Constitution when seceding from the Union). But instead of addressing the issue through legal routes, anti-slavery groups decided to fight the act subversively, supporting the Underground Railroad, defending slaves and helping them evade slave hunters and law enforcement.
Southern slave masters were none too thrilled by this and demanded that the act be enforced. The Supreme Court, which was heavy with Southerners, was appalled that the North was so defiant of the act. It ruled in the 1857 Dred Scott case that blacks -- free or slave -- were not citizens and so didn't have any rights to the freedoms stated in the Constitution. They could be returned to slavery no matter how long they had lived free [source: McPherson].
The Underground Railroad is often addressed separately from the Civil War, but there's a lot of evidence that its activities did much to precipitate the war. The Northwest Territory -- Ohio, Michigan, Illinois, Indiana, Wisconsin and part of Minnesota -- had never allowed slavery, so after the Dred Scott decision its residents often joined up with Northeastern abolitionists (as we learned earlier, nearly half of Underground Railroad workers were from Ohio). These anti-slavery groups formed political parties like the Free Soil party and the Republican Party, which would introduce Abraham Lincoln to the country. And the rest, as they say, is history.
So what happened when an escaped slave finally made it to the North? Read on to find out.