Castle Thunder, located in Richmond, Virginia, was a former tobacco warehouse located on Tobacco Row, converted into a prison used by the Confederacy to house civilian prisoners, including captured Union spies, political prisoners and those charged with treason during the American Civil War. A large number of its inmates were sentenced to death. Even though the inmates were sometimes allowed boxes of medicine and other supplies, the prison guards had a reputation for brutality. Another held for a time in this prison was Dr. Mary E. Walker, the only woman who ever received the Medal of Honor.