Johnson's Island, located in Sandusky Bay, Lake Erie was chosen as the site for the Union depot of captured Confederate officers in late 1861.
Johnson's Island, approximately 3 miles from Sandusky, was determined to be conveniently accessible for supplies needed for construction and maintenance of the prison and its population. It was also considered more easily protected than other islands in the open lake. The island could be leased for $500 a year with the government having control over who had access to the island. Because of these advantageous factors, the Federal Government built a prison designed to hold 2,500 prisoners on the island.
From April 1862 until the end of the war, Johnson's Island Civil War Military Prison functioned as the main Union depot for Confederate Officers. Designed to hold approximately 2500 prisoners of war, Johnson's Island eventually held up to 3200 at any one time. The overcrowding resulted in the construction of new latrines and to an expansion of the prison compound. Expansion of the prison facilities provides archaeologists with an opportunity to study changes in the physical structure of the prison as well as in the lifestyles of it's occupants. In comparison to the thirty-one Union prisons, Johnson's Island is unique in its purpose (housing Confederate Officers), in its military garrison (recruited specifically for guard duties) and in its condition (as an archaeological site).