Answer
During the early to mid-nineteenth century, the Underground Railroad was a covert network with concealed passageways and people who helped enslaved people escape. Enslaved African Americans primarily used the Underground Railroad to escape to free states and Canada.
What was the origin of the name "underground railroad"?
The explanation behind the name of the underground railroad was that anyone might take a passage on the secret network and vanish from public view as if they had just gone underground, which is how the Underground Railroad got its name.