The network of escape routes for enslaved african americans fleeing the south:

The Underground Railroad was the name of the escape routes used by slaves to escape the South and flee to the North. It was a network of special routes and safe houses that were used by both slaves and abolitionists who were sympathetic to their cause of escaping slavery. It started in the late 1700's and ended after the abolition of slavery. Canada was a popular destination, as slavery was prohibited their and had a longer border for easier access.