Casa Grande Ruins National Monument

Casa Grande Ruins National Monument ("Great House") and its surrounding compound as it may have appeared around 1350 C.E. One of the largest prehistoric structures ever built in North America, its purpose remains a mystery.Archeologists have discovered evidence that the ancient Sonoran Desert people who built the Casa Grande also developed wide-scale irrigation farming and extensive trade connections which lasted over a thousand years until about 1450 C.E.