There once was an invisible train that ran without tracks. This railroad transported slaves to freedom through a network of "stations" led by secret "conductors." George Washington noted the existence of these efforts as early as 1786. And by 1831, this growing freedom network was called the "Underground Railroad." Thousands of slaves found freedom through this human train in the 1800s.

Runaway slaves from the South would seek refuge in states where slavery was prohibited. Conductors on the railroad would hide escaped slaves in their homes and teach them secret codes and phrases to help them find the next safe house along the railroad. This continued until they reached freedom.

One of the most famous conductors along the Underground Railroad was Harriet Tubman, who was born into slavery, but through perseverance, was able to help herself and hundreds of others obtain freedom. After 25 years of slavery in Maryland, Harriet learned she was going to be separated from her family and sold, so she planned her escape. A neighbor told her of two houses where she would be safe. She traveled to the first house in the back of a wagon covered with a sack, and then made her way to Philadelphia on her own. Harriet described freedom as "heaven."

In Philadelphia, Harriet cooked and sewed to save enough money to rescue her family. She eventually helped 300 slaves gain freedom. Harriet became known as "Moses" because she ventured 19 times into the South or "Egypt." Harriet used music, Bible verses, and folklore to alert escaped slaves of danger and give them directions to safe houses.

During the Civil War, Harriet was a nurse to sick and wounded Union soldiers. She also taught newly-freed men and women how to care for themselves. In World War II, a ship was named in her memory, and in 1995, the federal government honored her accomplishments with a postage stamp.