But Tubman's joy at escaping slavery was muted, because her family had remained behind in servitude. "I was free, and they should be free," she later recalled thinking. She was determined to help them escape, too [source: Bradford].
After settling in Philadelphia, she worked as a hotel cook and saved her earnings to subsidize her secret career as a conductor on the Underground Railroad, a clandestine abolitionist network that had existed since the 1820s. It was a highly dangerous mission, since "slave stealers," as the Southern states called them, faced the risk of being publicly branded and jailed — and in Tubman's case, enslaved once more. And in 1850, Congress passed the Fugitive Slave Act, which made such efforts a federal crime [source: Allen].
That didn't stop Tubman. That same year, she slipped back into Maryland and helped her niece and her two children escape. Over the next decade, she repeated that mission a dozen more times, cautiously confining her efforts to farms that she knew on Maryland's Eastern Shore [source: Larson].
Tubman followed elaborate procedures to maintain stealth. She wore disguises, communicated with would-be escapees through third parties, and arranged for them to meet her miles away from their cabins, to reduce the chances that they would lead pursuers to her. And if all else failed, she carried a pistol. She warned her escapees that if they tried to turn back, she would shoot them to prevent them from betraying her and the rest [sources: Allen, Quinn].
As word got around of Tubman's successful missions, she became a sought-after speaker at abolitionist fundraising meetings. She also became a target of mercenary slave catchers. But their failure to apprehend her only added to her legend [source: Allen].
In 1860, Tubman pulled off an even more daring feat, by thwarting federal marshals in Troy, New York, who were attempting to send a captured slave named Charles Nalle back to Virginia. Tubman disguised herself as an elderly woman and slipped into a government building. When Nalle and his captors stepped out into the street, Tubman shouted a signal from an upper-story window, and a mob of abolitionists converged on them and seized Nalle, who was spirited away to a waiting riverboat [source: Winkler].