The daughter of a physician who believed in the equality of the sexes, Mary Edwards Walker graduated from Syracuse Medical College in 1855 at the age of 23. In keeping with her staunch abolitionist values, Walker was determined to serve her country when the Civil War broke out in 1861. The Army had no interest in hiring a female physician, but Walker was undaunted. After proving her worth as a contract surgeon, she was finally named an assistant surgeon of the 52nd Ohio Infantry. 

During her military service, Walker was noted for her willingness to cross over into Confederate territory to treat wounded civilians, regardless of their allegiance. Walker spent four months as a prisoner of war in a Confederate camp until, along with other medical prisoners, she was exchanged for Confederate doctors.

Walker wearing her Medal of Honor after the war

In 1865, Walker became the first-ever woman to be awarded a Congressional Medal of Honor. In her citation, President Andrew Johnson wrote:

"Whereas it appears from official reports that Dr. Mary E. Walker, a graduate of medicine, "has rendered valuable service to the Government, and her efforts have been earnest and untiring in a variety of ways," and that she was assigned to duty and served as an assistant surgeon in charge of female prisoners at Louisville, Ky., upon the recommendation of Major-Generals Sherman and Thomas, and faithfully served as contract surgeon in the service of the United States, and has devoted herself with much patriotic zeal to the sick and wounded soldiers, both in the field and hospitals, to the detriment of her own health, and has also endured hardships as a prisoner of war four months in a Southern prison while acting as contract surgeon; and Whereas by reason of her not being a commissioned officer in the military service, a brevet or honorary rank cannot, under existing laws, be conferred upon her; and Whereas in the opinion of the President an honorable recognition of her services and sufferings should be made. It is ordered, That a testimonial thereof shall be hereby made and given to the said Dr. Mary E. Walker, and that the usual medal of honor for meritorious services be given her."

In 1917, Walker received some bad news: the Army's criteria for awarding the Congressional Medal of Honor had changed, and her medal (along with almost a thousand others) had been officially rescinded. Undaunted, Walker continued to wear her medal every day until she died two years later. Though she didn't live to see it, Walker was vindicated when her medal was restored by President Jimmy Carter in 1977. She remains the only woman to ever receive the prestigious award.