What would be a good thesis concerning Harriet Tubman and the Underground Railroad?
Harriet Tubman overcame extraordinary adversity to become a historical figure, and so thesis statements about her early life would give a lot of material to work from. For example, she was put to work at age six, and from that moment on endured beatings and harsh conditions as she grew. You could write: "Because of her hard childhood, Harriet Tubman was well-prepared to overcome racism and brutality in her later years."
Another area is the unsympathetic view that other slaves had for her dreams; her first husband, John, was a free man but did not want to help Harriet become free. He claimed that his life was acceptable and there was no point inviting danger and the ire of slave-owners. You could write: "Despite the discouragement of those close to her, Harriet Tubman never stopped believing that she could be free."
Another area is the Underground Railroad, which was the route that Harriet took to escape slavery. She later became a "conductor" on the Railroad, helping other slaves escape; she claimed that over twenty missions, she never lost a "passenger" to surrender or betrayal. A good thesis for this topic might be: "Harriet Tubman's experience with slavery, and her knowledge of human nature gained through personal experience, made her a very effective ally to the Underground Railroad."
Harriet Tubman was an extremely strong woman who was able to overcome massive barriers in order to free as many slaves as she did. I would start by researching her past and early life. Not only was she a Civil Rights revolutionary, but she also had her own personal life and struggles. While she is most commonly known for her work on the Underground Railroad (which was in fact not underground at all and more like a series of safe houses), she was also an activist in many other ways, after her time given to the Underground Railroad as well as before. She also worked to help the Union Army as a spy, and after the war she worked to help poor former slaves as well as the elderly in her community. A good thesis to represent this might read something like this: Harriet Tubman was an activist for civil rights in many ways throughout her life. Three major ways in which she was able to leave her impact were through her efforts with the Underground Railroad, her work as a spy in helping the Union Army, and the dedication of her life to the impoverished and elderly black communities post-war.
I would look at Harriet Tubman's accomplishments as a conductor on the Underground Railroad. Harriet Tubman guided hundreds of slaves to freedom in the North, all while putting her life in danger. She was quite courageous in taking an active stance against slavery. The book you are referring to is a piece of young adult fiction, but it helps to make the life of Harriet Tubman quite approachable for younger readers. While parts of the book are speculative, most of it did actually happen, although dialogue has been changed in order to fit the story. One possible thesis is that Harriet Tubman: Conductor on the Underground Railroad tells the very inspiring story of Harriet Tubman, a woman who had the courage to do what she could to end slavery. You could also note the adversity that Tubman endured as a young slave and how this adversity made her an ideal candidate to lead groups of people North in dangerous conditions.