In 1892, President Benjamin Harrison set aside one square mile of Arizona Territory surrounding the Casa Grande Ruins as the first prehistoric and cultural reserve established in the United States. Thought to have been built around 1350 C.E. and abandoned around 1450 C.E. by the ancient people of the Hohokam period that had no written language so little is known of the people. We do know they established an intricate series of irrigation channels. The structures were built of caliche (calcium carbonate often used in arid regions). The outer structure of the "big house" was 3 stories, the inner was 4 stories. A connecting stagecoach route that ran right by the Casa Grande in the early 1890s resulted in much damage from souvenir hunting and vandalism. Great concern for the condition of the ruins called for a shelter to be built in 1903. Between 1937-1940 the C.C.C. (Civilian Conservation Corps) built the steel shelter that stands today.