This book is about Harriet Tubman. She was a slave in Maryland and went to Philadelphia for freedom. She went back to save other people, but when she heard that even if they were out of state they would be brought back to their master, so she decided to move everyone to Canada. She made 10-13 journeys saving people from slavery, and as long as they were with Harriet, they never got caught.
Fun fact: Harriet's original name was Araminta, and was called "Minty".