underground railroad

This gave rise to what was known as the Underground Railroad.

My father was one of the members of the Underground Railroad.

In those days, the Underground Railroad was in full operation.

And besides I must look after my underground railroad affairs.

The Underground Railroad was never coextensive with the abolition movement.

This act was designed to crush out the underground railroad.

Is there no "underground railroad" by which they may win their way to freedom?

I wouldn't wonder if this was the first trip on the Underground Railroad.

"The underground railroad is in fine working order," is the comment of The Journal.

Yet she was one of the most important agents of the Underground Railroad and a leader of fugitive slaves.