Cahokia (USA) - Massive Mississippian Center in the American Bottom

Prehistoric Capital City on the Mississippi River

Cahokia Mounds State Historic Site
The Cahokia Mounds State Historic Site preserves the burial mounds of an Indian civilization which inhabited the area from 900 to 1500 AD. | Location: Collinsville, Illinois, USA. Michael S. Lewis / Getty Images

Cahokia is the name of a large Mississippian (AD 1000-1600) agricultural settlement and mound group located within the enormous American Bottom floodplain of the Mississippi River at the junction of the Illinois and Missouri rivers in eastern Illinois state, in the mid-central United States.

Cahokia is the largest prehispanic site in North America north of Mexico, a proto-urban center with allied sites spread across the American Bottom.

During its heyday, the urban center of Cahokia covered an area of between 10-15 square kilometers (3.8-5.8 square miles), including nearly 200 earthen mounds arranged around vast open plazas, with thousands of pole and thatch houses, temples, pyramidal mounds and public buildings laid out in planned residential, political and ritual precincts. Cahokia was the main center of the Mississippian culture, with a population of about 20,000 people and trade connections throughout North America.


Cahokia's emergence as a regional center has been noted as early as AD 400, and by 1050 it emerged as a hierarchically-organized cultural and political center, inhabited by tens of thousands of people supported by native domesticates and maize.

  • Moorehead Phase (AD 1200-1350) decline and abandonment, sediment core studies have led some Munoz et al. to argue that Cahokia was abandoned as a result of flooding
  • Stirling Phase (AD 1100-1200), Cahokia controlled the American Bottom, the lower portions of the Missouri and Illinois river floodplains, and the adjacent hilly uplands, amounting to some 9,300 sq km (~3,600 sq mi)
  • Lohmann Phase (AD 1050-1100), population at 10,000-15,000 people, urban center at 14.5 sq km (5.6 sq mi); defensive palisades built surrounding at least 18 mounds including an area of 60-160 ha (.25-.6 sq mi)
  • Fairmount Phase (Terminal Late Woodland AD 900-1050), AB included local mound centers at Cahokia and the Lunsford-Pulcher site, 23 km (12 mi) to the south, population about 1,400-2,800
  • Late Woodland (AD 800-900) numerous small farming villages in the valley

There were three precincts in Greater Cahokia: Cahokia's grand plaza, with 120 platform and burial mounds, residential areas, specialized workshops and small plazas; the East St. Louis ceremonial precinct with ~50 mounds for special or high-status residential district; and the St. Louis ceremonial precinct with 26 mounds on the west side of the river, and provided access to the Ozark mountains. Within one day's walk of Cahokia were 14 subordinate mound centers and hundreds of small rural farmsteads.

Why Cahokia Blossomed

Cahokia was established around AD 1050, when people first built the Grand Plaza and the first stage of Monks Mound. It arose quickly, and within a century, Cahokia included more than 100 mounds within an area of about 1.8 sq km, at the eastern end of a 13 km-long continuum of habitation and mound groups across the floodplain.

Cahokia's location within the American Bottom was crucial to its success. Within the limits of the floodplain are thousands of acres of well-drained tillable land for farming, with abundant oxbow channels, marshes, and lakes that provided aquatic, terrestrial and avian resources.

Cahokia is also quite close to the rich prairie soils of the adjacent uplands where upland resources would have been available.

Evidence exists that Cahokia was a cosmopolitan center, with people migrating in from different regions and access to a broad trading network from the gulf coast and southeast to the trans-Mississippi south, especially the Caddoans of the Arkansas River, the eastern plains, the upper Mississippi valley and the Great Lakes. Cahokians dabbled in long-distance trade of marine shell, shark teeth, pipestone, mica, Hixton quartzite, exotic cherts, copper, and galena.

Main Features: Monks Mound and Grand Plaza

Said to have been named after the monks who were using the mound in the 17th century, Monks Mound is the largest of the mounds at Cahokia, a quadrilateral flat-topped, earthen pyramid that supported a series of buildings on its upper level.

It took about 720,000 cubic meters of earth to construct this 30 meters (100 feet) tall, 320 m (1050 ft) north-south and 294 m (960 ft) east-west behemoth. Monks Mound has four flat surfaces or terraces, two of which were built to support wooden buildings.

Estimated at between 16-24 hectares (40-60 acres), the Grand Plaza was marked by Monks Mound on the north and Round Top and Fox mounds on the south. A string of smaller mounds mark its east and west sides. Scholars believe it was first used as a source of soil for mound construction, but then it was purposefully leveled off, beginning at the end of the eleventh century. A wooden palisade enclosed the plaza during the Lohmann phase. It took an estimated labor of 10,000 person hours to build even 1/3-1/4 of the entire plaza, making it one of the largest construction projects at Cahokia.

The plaza featured a number of tall wooden marker posts; and there public rituals and feasts were held several times during the year, based on a large midden identified under one of the later mounds near the plaza. Rituals held in summer and fall involved the use of tobacco, red cedar, and pigments, and enormous quantities of cooking jars and food remains.

Mound 72

Mound 72 was a mortuary temple/charnel house, one of several used by the Mississippians at Cahokia, but it stands out because of the 272 burials found in 25 separate burial contexts within the mound and dated between about 1050-1150 AD). The two highest ranking individuals found were two males buried together with 12 retainers. The men were laid out with four retainers and on top of a blanket or platform made of between shell-beads. The blanket is one of the more remarkable artifacts found at Cahokia, made of over 12,000-20,000 marine shell beads laid out in the shape of a falcon or eagle.

Four mass graves held a total of 118 individuals, which were initially reported as all female, but have been found to just mostly female; and another grave of four headless and handless men was also identified within Mound 72.

Mound 34 and Woodhenges

Mound 34 at Cahokia was occupied during the Moorehead phase of the site, and while it's neither the largest or most impressive of mounds, it held evidence of a copper workshop, a nearly unique set of data on the hammered copper process used by the Mississippians. Metal smelting was not known in North America at this time, but copper working, consisting of a combination of hammering and annealing, was part of the entrenched techniques.

Eight pieces of copper were retrieved from Mound 34 backfill, and sheet copper covered in black and green corrosion product. All of the pieces are abandoned blanks or scraps, not the finished product. Chastain and colleagues examined the copper and ran experimental replications, and concluded that the process involved large pieces of native copper were reduced into thin sheets through repeated cycles of hammering and annealing, by exposure to an open wood fire for a few minutes.


Four or perhaps five massive circles or arcs of large postholes called "Wood Henges" or "post circle monuments" were found in Tract 51; another has been found near Mound 72. These have been interpreted as solar calendars, marking the solstices and equinoxes and no doubt the focus of community rituals.


This article is part of the guide to Mississippian, and part of the Dictionary of Archaeology