Casa Grande Ruins National Monument, in Coolidge, Arizona, just northeast of the city of Casa Grande, preserves a group of Hohokam structures dating to the Classic Period (1150-1450 C.E.).  The national monument consists of the ruins of multiple structures surrounded by a compound wall constructed by the ancient people of the Hohokam period, who farmed the Gila Valley in the early 13th century. 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. "Casa Grande" is Spanish for "big house" (Siwañ Wa'a Ki: in O'odham); these names refer to the largest structure on the site, which is what remains of a four-story structure that may have been abandoned by 1450. The structure is made of caliche (caliche is a layer of soil in which the individual soil particles are cemented together with calcium carbonate), and has managed to survive the extreme weather conditions for about seven centuries. The large house consists of outer rooms surrounding an inner structure. The outer rooms are all three stories high, while the inner structure is four stories high. The structures were constructed using traditional adobe processes.