Question

The system of escape routes and hiding places for runaway slaves.

Answer 1

The Underground Railroad

Answer 2

The system of escape routes and hiding places for runaway slaves was known as Underground Railroads.
In the US, slavery led to the creation of such escape routes and safe houses in order to help slaves escape and lead a normal life after that. They would either run to Canada or free states within America which abolished slavery. One of the most famous leaders was Harriet Tubman.