During the Civil War, the courthouse became a major headquarters for the Union Army. This included the establishment of federal provost marshal's office in 1862, which replaced civil courts, giving him the authority to conduct investigations and enforce federal law. As a result, Confederate soldiers and supporters of the Southern cause were imprisoned here in a jail built behind the building. Provost marshals had a lot of power since they were generally not overseeing by anyone of any legal body. They could even declare martial law.