An unhappy childhood helped Dorothea Dix to identify with society's outcasts. Like many young women of her day, she became a school teacher. Surrounded by the ferment of reform in pre-Civil War Boston but untouched by it, she was drifting towards a life of spinsterly aimlessness until one cold day in March 1841. She had volunteered to teach a Sunday school class at the jail in East Cambridge. Among the convicts, shivering in an unheated room, she found some women who were mentally ill. Why was there no stove to warm them, she demanded? Lunatics, she was told, could not feel the cold, and they would only burn themselves or set the building afire. Dorothea Dix determined to act; she had found her cause.

She spent over a year touring every jail, whorehouse, and house of correction in Massachusetts. She then presented a report, or "memorial" to the Legislature asking for funds for an institution specially designed to treat the mentally ill. She did the same in state after state, traveling thousands of miles alone and publicizing the terrible conditions she found. Always observing the rules of feminine propriety, she rarely spoke publicly, but she was a persuasive lobbyist behind the scenes.

When the Civil War broke out she was appointed superintendent of nurses for the Union Army. Unfortunately, this was a role for which she was ill-suited, and controversy swirled around her. After the war she toured hospitals in the South and in Europe, slowing up but never abandoning her role as crusader for humane treatment of the insane.