Mississippian-culture sites from Wisconsin (see Aztalan State Park) to the Gulf Coast, and from Florida to Arkansas and Oklahoma. The SECC was frequently tied into ritual game-playing, as with chunkey. The Mississippians had no writing system or stone architecture. They worked naturally occurring metal deposits, such as hammering and annealing copper for ritual objects such as Mississippian copper plates and other decorations, but did not smelt iron or practice bronze metallurgy. Chronology The Mississippian stage is usually divided into three or more chronological periods. Each period is an arbitrary historical distinction varying regionally. At a particular site, each period may be considered to begin earlier or later, depending on the speed of adoption or development of given Mississippian traits. The "Mississippian period" should not be confused with the "Mississippian culture". The Mississippian period is the chronological stage, while Mississippian culture refers to the cultural similarities that characterize this society. The Early Mississippian period (c. 1000–1200 CE) had just transitioned from the Late Woodland period way of life (500–1000). Different groups abandoned tribal lifeways for increasing complexity, sedentism, centralization, and agriculture. Production of surplus corn and attractions of the regional chiefdoms led to rapid population concentrations in major centers. The Middle Mississippian period (c. 1200–1400) is the apex of the Mississippian era. The expansion of the great metropolis and ceremonial complex at Cahokia (in present-day Illinois), the formation of other complex chiefdoms, and the spread and development of SECC art and symbolism are characteristic changes of this period. The Mississippian traits listed above came to be widespread throughout the region. The Late Mississippian period (c. 1400–1540) is characterized by increasing warfare, political turmoil, and population movement. The population of Cahokia dispersed early in this period (1350–1400), perhaps migrating to other rising political centers. More defensive structures are often seen at sites, and sometimes a decline in mound-building and large-scale, public ceremonialism. Although some areas continued an essentially Middle Mississippian culture until the first significant contact with Europeans, the population of most areas had dispersed or were experiencing severe social stress by 1500. Along with the contemporaneous Ancestral Pueblo peoples, these cultural collapses coincide with the global climate change of the Little Ice Age. Scholars theorize drought and the reduction of maize agriculture, together with possible deforestation and overhunting by the concentrated populations, forced them to move away from major sites. This period ended with European contact in the 16th century. Regional