The significance of Harriet Tubman in the Underground Railroad lies in her role as a courageous leader and conductor who helped enslaved individuals escape to freedom. Tubman, born into slavery, escaped herself and later made numerous trips back to the South, guiding over 300 enslaved people to safety using a network of secret routes and safe houses. Her bravery and determination not only exemplified the fight against slavery but also inspired future generations in the struggle for civil rights and freedom, solidifying her as an emblem of resilience and courage.