Camp Rupert was the largest prisoner of war camp in Idaho. Housing some 4000 POWs, most were German and Italian. The camp was built at an initial cost of $500,000 and maintained by nearly 1000 army personnel and civilians. Over 170 buildings were constructed on 300 acres, including a field house, hospital, mess halls, barracks, chapel, commissaries, large warehouses, and recreation centers. It also served as a base camp for 24 branch camps in Idaho, Oregon, and Montana.