March 10, 2013, will mark the 100th anniversary of the death of Harriet Tubman, a fearless conductor on the Underground Railroad. She is greatly admired for her bravery in guiding slaves to freedom and for her generous spirit. But for many years, her story was in danger of being forgotten.

When Harriet was a slave in Maryland, her owner hired her out at 7 years old to do housework. She later worked on a farm plowing fields and chopping wood. But she was determined to be free. One night, when she was 27, she escaped — traveling north to Philadelphia, Pennsylvania, mostly by walking at night. During the day, she would sleep in the woods on a bed of pine needles.

Between 1850 and 1860, Harriet helped other slaves, including family and friends, escape north to freedom. She had to disguise her identity and take enormous risks, but she was never captured....