Hohokam great houses and the collapse of the canal towns

By 1300, archaeologists say, Hohokam irrigation supported the largest population in the American Southwest. In the Civano phase (from 1300 to 1350 or 1375) villages were reorganised into compact clusters of five to twenty-five adobe-walled compounds grouped around one large compound with a platform mound or a great house. Great houses of up to four storeys were built only in the largest communities and were probably used by managerial or religious elites, perhaps also aligned for astronomical observation. Salado polychrome pottery spread, jewellery reached its finest workmanship, burial replaced cremation north of the Gila, and trade with Mexico declined while goods from the Pueblo peoples to the north and east grew more common.

The great house of Casa Grande, near today’s Coolidge, stood at the heart of the largest Hohokam community of the middle Gila valley, which by 1300 comprised about nineteen walled compounds, a platform mound, the great house and many refuse mounds. Built of caliche earth, it has outer rooms three storeys high around a four-storey core. According to Akimel O'odham tradition, recorded in the early 20th century, it was built by a chief called Sial Teu-utak, ‘Turquoise Leader’. After the middle of the 14th century the settlement declined quickly and was abandoned around 1400 or 1450; Father Eusebio Kino found the great house deserted and decaying in 1694, and in 1892 it became the first prehistoric reserve in the United States.

Between about 1350 and 1375 the Hohokam tradition lost its stability. Repeated floods in the mid-14th century deepened the bed of the Salt River and destroyed the heads of the canals; the canals were extended upstream, but new floods washed out the extensions, leaving networks hundreds of miles long useless, and the systems on the Gila were abandoned as well. After 1375 most villages and canals of the lower Salt valley were given up. The people did not vanish — the fall in population is now thought to have been smaller than once believed — but scattered into small villages, mostly along the Gila, in what archaeologists see as a critical stage in the emergence of the modern O'odham.