Excerpt:
They were the master farmers of America's Southwest, and engineers of great networks of irrigation canals in the Salt River Valley. They first appeared about 350 B.C., building canals of open ditches, gouged out with stone tools and wooden hoes. The canals spanned almost 250 miles, stimulating trade and commerce between communities of hundreds and thousands of people. No one knows why, whether by climatic upheaval, drought or floods, the Hohokams suddenly vanished in 1450 A.D., well before Columbus discovered America or the Pilgrims landed at Plymouth Rock.