Cahokia

A map showing approximate areas of various Mississippian and related cultures. Cahokia is located near the center of this map in the upper part of the Middle Mississippi area.

Although some evidence exists of occupation during the Late Archaic period (around 1200 BCE) in and around the site,[9] Cahokia as it is now defined was settled around 600 CE during the Late Woodland period. Mound building at this location began with the emergent Mississippian cultural period, around the 9th century CE.[10] The inhabitants left no written records beyond symbols on pottery, shell, copper, wood, and stone, but the elaborately planned community, woodhenge, mounds, and burials reveal a complex and sophisticated society.[11]

The city's complex construction of earthen mounds required digging, excavation and transportation by hand using woven baskets. Construction made use of 55 million cubic feet (1.6 million cubic meters) of earth, and much of the work was accomplished over a matter of decades. Its highly planned large, smoothed-flat, ceremonial plazas, sited around the mounds, with homes for thousands connected by laid out pathways and courtyards, suggest the location served as a central religious pilgrimage city.[12]

The city's original name is unknown. The mounds were later named after the Cahokia tribe, a historic Illiniwek people living in the area when the first French explorers arrived in the 17th century.[13] As this was centuries after Cahokia was abandoned by its original inhabitants, the Cahokia tribe was not necessarily descended from the earlier Mississippian-era people. Most likely, multiple indigenous ethnic groups settled in the Cahokia Mounds area during the time of the city's apex.[14][15]

Historian Daniel Richter notes that the apex of the city occurred during the Medieval Warming Period. This period appears to have fostered an agricultural revolution in upper North America, as the three-fold crops of maize, beans (legumes), and gourds (squash) were developed and adapted or bred to the temperate climates of the north from their origins in Mesoamerica. Richter also notes that Cahokia's advanced development coincided with the development in the Southwest of the Chaco Canyon society, which also produced large-scale works in an apparent socially stratified society. The decline of the city coincides with the Little Ice Age, although by then, the three-fold agriculture remained well-established throughout temperate North America.[16]

Artist's recreation of central Cahokia. Cahokia's east–west baseline transects the Woodhenge, Monk's Mound, and several other large mounds.

Cahokia became the most important center for the Mississippian culture. This culture was expressed in settlements that ranged along major waterways across what is now the Midwest, Eastern, and Southeastern United States. Cahokia was located in a strategic position near the confluence of the Mississippi, Missouri, and Illinois rivers. It maintained trade links with communities as far away as the Great Lakes to the north and the Gulf Coast to the south, trading in such exotic items as copper, Mill Creek chert,[17] and whelk shells.

Mill Creek chert, most notably, was used in the production of hoes, a high demand tool for farmers around Cahokia and other Mississippian centers. Cahokia's control of the manufacture and distribution of these hand tools was an important economic activity that allowed the city to thrive.[18] Mississippian culture pottery and stone tools in the Cahokian style were found at the Silvernale site[19] near Red Wing, Minnesota, and materials and trade goods from Pennsylvania, the Gulf Coast, and Lake Superior have been excavated at Cahokia. Bartering, not money, was used in trade.[20]

At the high point of its development, Cahokia was the largest urban center north of the great Mesoamerican cities in Mexico and Central America. Home to about 1,000 people before circa 1050, its population grew rapidly after that date. According to a 2007 study in Quaternary Science Reviews, "Between AD 1050 and 1100, Cahokia's population increased from between 1,400 and 2,800 people to between 10,200 and 15,300 people".[21] an estimate that applies only to a 1.8-square-kilometre (0.69 sq mi) high-density central occupation area.[22] Archaeologists estimate the city's population at between 6,000 and 40,000 at its peak,[23] with more people living in outlying farming villages that supplied the main urban center.

As a result of archeological excavations in the early 21st century, new residential areas were found to the west of Cahokia; this discovery increased estimates of historic area population.[23] If the highest population estimates are correct, Cahokia was larger than any subsequent city in the United States until the 1780s, when Philadelphia's population grew beyond 40,000.[24] Its population may have been larger than contemporaneous London[25] and Paris.[26]

One of the major problems that large centers like Cahokia faced was keeping a steady supply of food. A related problem was waste disposal for the dense population, and Cahokia is believed to have become unhealthy from polluted waterways. Because it was such an unhealthy place to live, Snow believes that the town had to rely on social and political attractions to bring in a steady supply of new immigrants; otherwise, the town's death rate would have caused it to be abandoned earlier.[18]

Mississippian period showing the multiple layers of mound construction, mound structures such as temples or mortuaries, ramps with log stairs, and prior structures under later layers, multiple terraces, and intrusive burials

The population of Cahokia began to decline during the 13th century, and the site was abandoned by around 1350.[27][28] Scholars have proposed environmental factors, such as environmental degradation through overhunting, deforestation[29] and pollution,[30] and climatic changes, such as increased flooding[31] and droughts,[32][33] as explanations for abandonment of the site. However, more recent research suggests that there is no evidence of human-caused erosion or flooding at Cahokia.[34][35][27]

Political and economic problems may also have contributed to the community's decline.[36] It is likely that social and environmental factors combined to produce the conditions that led people to leave Cahokia.[37][33]

Another possible cause is invasion by outside peoples, though the only evidence of warfare found is defensive wooden stockade and watchtowers that enclosed Cahokia's main ceremonial precinct. There is no other evidence for warfare, so the palisade may have been more for ritual or formal separation than for military purposes. Diseases transmitted among the large, dense urban population are another possible cause of decline. Many theories since the late 20th century propose conquest-induced political collapse as the primary reason for Cahokia's abandonment.[38]

Together with these factors, researchers found evidence in 2015 of major floods at Cahokia, so severe as to flood dwelling places. Analysis of sediment from beneath Horseshoe Lake has revealed that two major floods occurred in the period of settlement at Cahokia, in roughly 1100–1260 and 1340–1460.[39][40] While flooding may have occurred early in the rise of the city, it seems not to have deterred the city builders; to the contrary, it appears they took steps such as creating channels, dykes, and levees that protected at least the central city throughout its inhabited history.[34]

An 1882 illustration of Monks Mound showing it with fanciful proportions

Incised sandstone tablet of a Birdman found in 1971 during excavations into the east side of Monks Mound

Monks Mound is the largest structure and central focus of the city: a massive platform mound with four terraces, 10 stories tall, it is the largest man-made earthen mound north of Mexico. Facing south, it is 100 ft (30 m) high, 951 ft (290 m) long, 836 ft (255 m) wide and covers 13.8 acres (5.6 ha).[41] It contains about 814,000 cu yd (622,000 m³) of earth.[18] The mound was built higher and wider over the course of several centuries, through as many as 10 separate construction episodes, as the mound was built taller and the terraces and apron were added.[41]

Monks Mounds was named for the community of Trappist monks who resided there for a short time, after Euroamericans settled in the area. Excavation on the top of Monks Mound has revealed evidence of a large building, likely a temple or the residence of the paramount chief, which would have been seen throughout the city. This building was about 105 ft (32 m) long and 48 feet (15 m) wide, and could have been as much as 50 ft (15 m) high. It was about 5,000 sq ft (460 m²).

The east and northwest sides of Monks Mound were twice excavated in August 2007 during an attempt to avoid erosion due to slumping. These areas were repaired to preserve the mound.[42]

Early in its history, Cahokia underwent a massive construction boom. Along with the early phase of Monks Mound, an overarching urban layout was established at the site. It was built with a symbolic quadripartite worldview and oriented toward the four cardinal directions with the main east–west and north–south axes defined with Monks Mound near its center point. Four large plazas were established to the east, west, north, and south of Monks Mound.[43][44]

To the south of Monks Mound is the Grand Plaza, a large area that covered roughly 50 acres (20 ha) and measured over 1,600 ft (490 m) in length by over 900 ft (270 m) in width. Researchers originally thought the flat, open terrain in this area reflected Cahokia's location on the Mississippi's alluvial flood plain, but instead soil studies have shown that the landscape was originally undulating ridge and swale topography. In one of the earliest large-scale construction projects, the site had been expertly and deliberately leveled and filled by the city's inhabitants. It is part of the sophisticated engineering displayed throughout the site.[45] It was used for large ceremonies and gatherings, as well as for ritual games, such as chunkey. The game was played by rolling a disc-shaped chunky stone across the field. The players would throw spears where they thought the chunky stone would land. The game required a great deal of judgment and aim.[18]

The major ceremonial north–south 'axis' connects the main precinct with the large ridgetop mortuary mound to its south now known as the Rattlesnake Mound (Mound 66[46]). The feature, named the Rattlesnake Causeway by archaeologists, was an elevated embankment about 18 metres (59 ft) wide, roughly 800 metres (2,600 ft) in length and varies in height from 0.5 metres (1.6 ft) to almost 1.3 metres (4.3 ft) as it traverses a low swampy area to the south of the Grand Plaza.[47] It is aligned 5° east of north, a direction thought to mimic the maximum southern moon rise of 5° west of north, albeit in reverse. This is thought to have had symbolic associations to the builders in connection with their lunar maize goddess of the underworld.[48] This is further strengthened by its close proximity to the ridgetop mortuary Mound 72, the underworld connotations of the low water-filled area the causeway traversed, and its terminus at the mortuary complex at the Rattlesnake Mound. The causeway itself may have been seen as a symbolic "Path of Souls".[47]

The high-status central district of Cahokia was surrounded by a 2-mi-long palisade that was equipped with protective bastions. A later addition to the site, when the palisade was constructed, it cut through and separated some pre-existing neighborhoods.[18] Archaeologists found evidence of the stockade during excavation of the area and indications that it was rebuilt several times. Its bastions showed that it was mainly built for defensive purposes.[18]

Beyond Monks Mound, as many as 120 more mounds stood at varying distances from the city center. To date, 109 mounds have been located, 68 of which are in the park area. The mounds are divided into three different types: platform, conical, and ridge-top. Each appeared to have had its own meaning and function. In general terms, the city center seems to have been laid out in a diamond-shaped pattern about 1 mi (1.6 km) from end to end, while the entire city is 5 mi (8.0 km) across from east to west.

Mound 72

During excavation of Mound 72, a ridge-top burial mound south of main urban precinct, archaeologists found the remains of a man in his 40s who was probably an important Cahokian ruler. The man was buried on a bed of more than 20,000 marine-shell disc beads arranged in the shape of a falcon,[49] with the bird's head appearing beneath and beside the man's head, and its wings and tail beneath his arms and legs.

The falcon warrior or "birdman" is a common motif in Mississippian culture. This burial clearly had powerful iconographic significance. In addition, a cache of sophisticated, finely worked arrowheads in a variety of different styles and materials was found near the grave of this important man. Separated into four types, each from a different geographical region, the arrowheads demonstrated Cahokia's extensive trade links in North America.

Archeologists recovered more than 250 other skeletons from Mound 72. Scholars believe almost 62% of these were sacrificial victims, based on signs of ritual execution, method of burial, and other factors.[50] The skeletons include:

• Four young males, missing their hands and skulls
• A mass grave of more than 50 women around 21 years old, with the bodies arranged in two layers separated by matting
• A mass burial containing 40 men and women who appear to have been violently killed, some of these may have been buried alive: "From the vertical position of some of the fingers, which appear to have been digging in the sand, it is apparent that not all of the victims were dead when they were interred – that some had been trying to pull themselves out of the mass of bodies."[51]

The relationship of these burials to the central burial is unclear. They were unlikely to have all deposited at the same time. Wood in several parts of the mound has been radiocarbon-dated to between 950 and 1000 CE.

Excavations have indicated that Mound 72 was not constructed as a single mound, but rather as a series of smaller mounds. These mounds were reshaped and covered over to give Mound 72 its final ridge-top shape.[52]

Mississippian culture repoussé copper plates

Excavations near Mound 34 from 2002 to 2010 revealed a copper workshop. This unique find was originally discovered in the 1950s by archaeologist Gregory Perino, but its exact location was lost for 60 years. It is the only known copper workshop to be found at a Mississippian culture site.[53] The area contains the remains of three tree stumps thought to have been used to hold anvil stones. Analysis of copper found during excavations showed that it had been annealed, a technique involving repeatedly heating and cooling the metal as it is worked, as blacksmiths do with iron.[53]

Artisans produced religious items, such as long-nosed god maskettes, ceremonial earrings with a symbolic shape, thought to have been used in fictive kinship rituals.[54][55] Many of the stylistically related Mississippian copper plates, such as the Wulfing cache from southeastern Missouri, some of the Etowah plates from Georgia, and many of the Spiro plates from Oklahoma, are associated with the Greater Braden style and are thought to have been made in Cahokia in the 13th century.[56][57][58][59]

View of the reconstructed Woodhenge III and its alignment with the equinox pole and Monks Mound 0.5 miles (0.8 km) away

The Cahokia Woodhenge was a series of large timber circles located roughly 850 m (2,790 ft) to the west of Monks Mound. They are thought to have been constructed between 900 and 1100 CE, with each one being larger and having 12 more posts than its predecessor.[60] The site was discovered during salvage archaeology undertaken by Dr. Warren Wittry in the early 1960s interstate highway construction boom. Although the majority of the site contained village house features, a number of unusually shaped, large post holes were also discovered. When the holes were plotted out, they formed several arcs of equally spaced holes.[61] Detailed analytical work supported the hypothesis that the placement of these posts was by design,[62] and Wittry hypothesized that the arcs could be whole circles. He began referring to the circles as "woodhenges", comparing the structures to England's well-known circles at Woodhenge and Stonehenge.[63][64]

Additional excavations in the 1960s–1980s used predictions based on verified posthole locations and spacing to locate other postholes and confirm the existence of five separate timber circles in the general vicinity. The circles are now designated Woodhenges I through V in Roman numerals.[61] In 1985, a reconstruction of Woodhenge III was built with the posts being placed into the original excavated post positions.[61] The circle, which has 48 posts in the circle and a 49th central post, has been used to investigate archaeoastronomy at Cahokia.[65] The Illinois Historic Preservation Division that oversees the Cahokia site hosts public sunrise observations at the vernal and autumnal equinoxes and the winter and summer solstices. Out of respect for Native American beliefs, these events do not feature ceremonies or rituals of any kind.[66][67][68]