Encyclopedia of the Underground Railroad

Fugitive slaves were reported in the American colonies as early as the 1640s, and escapes escalated with the growth of slavery over the next 200 years. As the number of fugitives rose, the Southern states pressed for harsher legislation to prevent escapes. The Fugitive Slave Act of 1850 criminalized any assistance, active or passive, to a runaway slave--yet it only encouraged the behavior it sought to prevent.