Born in 1832, Mary Edwards Walker was not only a physician, but a surgeon, at a time when women, frankly, weren't respected enough to even be admitted to medical school, let alone practice.
That wasn't enough. In time, Walker was also a feminist, a prohibitionist, and an abolitionist — clearly, no one who stepped back from a righteous fight. She was a schoolteacher for a time, and shocked colleagues and parents by wearing trousers, though often under a knee-length skirt. Pants, she knew, were just more practical.
She maintained a private medical practice for many years, and when the Civil War broke out she volunteered her services to the Union Army. They turned her down, but offered to let her function as a nurse. She declined and volunteered as a spy, but was rejected again, serving as an unpaid civilian surgeon until she was finally hired as a civilian surgeon in 1863.