Cahokia

Cahokia lies in Illinois, across the Mississippi from St. Louis. People were living there by about 600, and mound building began around the 9th century. Around 1050 a planned city was laid out, oriented to the north along a Grand Plaza, and between 1050 and 1150 it may have had 10,000 to 20,000 inhabitants. At its height it covered nearly 1,600 ha with some 120 mounds, and its people traded for copper, shark teeth and shells with communities from the Great Lakes to the Gulf Coast.

At its centre stood Monks Mound, begun in the first half of the 10th century and raised to about 30 m, with a building more than 30 m long on its summit. In Mound 72 archaeologists found the remains of about 270 people, among them a man laid on some 10,000 shell beads arranged in the shape of a falcon. Around 1175 a palisade was built around the core, but people began leaving in the late 12th century, and by the 14th century the city was abandoned.

The city's own name is unknown; the mounds are named after the Cahokia, an Illiniwek people living in the area when French explorers arrived in the 17th century. Nearly all the mounds across the river in St. Louis were levelled for fill in the mid-19th century. Illinois first protected the site in 1923, when its legislature authorised the purchase of a state park, and highway building in the 1950s both damaged the site and paid for large rescue excavations. Cahokia was inscribed as a World Heritage site in 1982.