Iron Mountain divisional camp was established at this site in the spring of 1942 as one of eleven camps built in the California-Arizona desert to harden and train United States troops for service on the battlefields of World War II. The first major unit trained here was the 3rd Armored Division, followed by elements of the 4th, 5th, 6th, and 7th Armored Divisions. In all, one million men trained in the desert before the training center was officially closed in May of 1944. The camp's most unique feature is the huge relief map built into the desert floor, which can still be seen.