Johnson's Island is a 300-acre (120 ha) island in Sandusky Bay, located on the coast of Lake Erie, 3 miles (4.8 km) from the city of Sandusky, Ohio. It was the site of a prisoner-of-war camp for Confederate officers captured during the American Civil War. Initially, Johnson's Island was the only Union prison exclusively for Confederate officers but eventually held privates, political prisoners, persons sentenced to court martial and spies. Civilians who were arrested as guerrillas, or bushwhackers, were also imprisoned on the island. During its three years of operation, more than 15,000 men were incarcerated there.