The Underground Railroad "UGR" (1780-1862)  was neither "underground" nor  a "railroad". It was a way of  assisting slaves to freedom prior to and during the Civil War. It included a whole network of people who assisted slaves in running away from their slave owners in the southern states. Their journeys took them  up through northern states and to freedom in Canada.
Visit site http://www.smithsonianmag.si.edu/smithsonian/issues96/oct96/undergroundrr.html for more information on Harriet Tubman.

    The journey had to be taken in utmost secrecy. The railroad became the symbol of the slaves "flight to freedom" perhaps because of the railroads growing popularity at the time. Railroad terms were used throughout the transportation process.

    Many sympathizers and activists aided the slaves in their escape to freedom. Harriet Tubman is perhaps the best known "conductor" of the UGR. During a ten year period, she made 19 trips and led over 300 slaves to freedom.
Visit site http://www2.lhric.org/pocantico/tubman/tubman.html for information on Harriet Tubman.