Harriet Tubman was an extraordinary African-American woman who freed herself from slavery by running away from Maryland to Philadelphia in 1849. In 1850, when the Fugitive Slave Act made it illegal to help a runaway slave, Tubman decided to join the "Underground Railroad," the network of people who helped slaves to their freedom.
The Underground Railroad was an elaborate and secret series of houses, tunnels and roads set up by abolitionists and former slaves as a way out of the South. Tubman knew these routes so well that she was never captured and never failed to deliver her "passengers" to safety.
She guided 300 slaves through the Underground Railroad in the years leading up to the Civil War. In 1861, when the Civil War began, she served as a nurse, spy and scout for the Union forces. Well acquainted with the countryside from her days as a "conductor" on the Underground Railroad, she was considered especially valuable as a scout.