What was known during the Civil War as Gratiot Street Military Prison was originally the McDowell Medical College. It was a large octagonal building, built of gray stone, and stood at the corner of Eight and Gratiot Streets. It was flanked by two wings, the southern situated directly on the corner of eight and Gratiot Streets, and the northern extending to the building of the Christian Brothers. It was appropriated by the military authorities at the beginning of the war for use as a military prison, and to it were committed from time to time captured Confederate soldiers, Southern sympathizers placed under arrest, and those charged with being "bush-whackers," spies or mail-carriers, and also deserters, bounty-jumpers, and delinquents from the Unions side. many prominent citizens of Missouri were incarcerated in this prison, among them being men who had occupied high public stations and who had rendered important services to the country, but whose overt acts or openly expressed sympathy with the Confederate cause occasioned their imprisonment. The discipline maintained in the prison seems to have been severe, and there were many complaints of harsh treatment and of unnecessary hardships imposed upon those who had the misfortune to incur the displeasure of the military authorities in complete control of the city.
Encyclopedia of the History of St. Louis, 1899