This thesis discusses Stephen Sondheim's 1979 musical adaptation of the novel that originated the story of Sweeney Todd in 1846, The String of Pearls. Sondheim's musical has been lastingly popular with its American audience despite the story's British roots, due in large part to the American innovation of the tale. Sondheim's Americanization emphasizes several themes, already staples of American culture as evidenced by trends in popular cultural artifacts such as Batman, which speak to American audiences and allow them to connect with the British story of Sweeney Todd. In Sondheim's transformation, the villainous Sweeney Todd becomes a complex lover, along with his companion characters, and he is driven to extremes by love and his deprivation of it. Sondheim also exploits the filthy Victorian setting of the story to relate directly to his immediate New York audience and underscore trends of corruption in its real-world judicial system, as well as that of the fictional London. This corruption becomes a problem Americans cannot stand to see unsolved, and Sweeney Todd transforms under Sondheim's hand into a vigilante hero the likes of the already beloved Dark Knight, highlighting an optimistic and essentially American skepticism of tragedy and belief in the power of individuals to effect change.