GEOS 220: Environmental History of Southwest
Human Chronology

15,000 years bp humans arrive in North America encountered megafauna
5500 BC to 500 BC Archaic hunters and gatherers, generalists
2000 BC beginning of agriculture in the SW introduction of cultigens from Mesoamerica
AD 500 beginning of sedentary prehistoric cultures Anasazi, Hohokam, Mogollon, Sinagua, Pueblos
AD 1130-1150 Chaco Canyon abandoned drought
AD 1300 Mesa Verde, Kayenta, northern Sinagua abandoned Great Drought
by AD 1350 Mogollon abandoned drought
by AD 1400 Hohokam abandoned drought/flooding
AD 1450 Athapaskan immigration Navajo and Apache
AD 1540 first Spanish contact Coronado Entrada
AD 1598 to 1821 Spanish colonization and rule European livestock, crops
AD 1821 to 1848 Mexican rule grazing rancheros in AZ
AD 1848 Mexican-American War,
begin United States rule
Much of SW becomes part of USA
AD 1854 Gadsden Purchase land south of the Gila River acquired by US
AD 1912 statehood for both New Mexico (47th) and Arizona (48th) last states of continental US

Laboratory of Tree-Ring Research, The University of Arizona
Tucson, Arizona 85721 USA
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