Cahokia

The Cahokia Mounds State Historic Site (11 MS 2) is the site of a pre-Columbian Native American city (which existed c.  1050–1350 CE) directly across the Mississippi River from present-day St. Louis, Missouri. This historic park lies in south-western Illinois between East St. Louis and Collinsville. The park covers 2200 acre, or about 3.5 sqmi, and contains about 80 manmade mounds, but the ancient city was much larger. At its apex around 1100 CE, the city covered about 6 sqmi, included about 120 earthworks in a wide range of sizes, shapes, and functions, and had a population of between 15,000 and 20,000 people.

Cahokia was the largest and most influential urban settlement of the Mississippian culture, which developed advanced societies across much of what is now the Central and the Southeastern United States, beginning more than 1,000 years before European contact. Today, the Cahokia Mounds are considered to be the largest and most complex archaeological site north of the great pre-Columbian cities in Mexico.

Cahokia Mounds is a National Historic Landmark and a designated site for state protection. It is also one of the 25 UNESCO World Heritage Sites within the United States. The largest prehistoric earthen construction in the Americas north of Mexico, the site is open to the public and administered by the Illinois Historic Preservation Division and supported by the Cahokia Mounds Museum Society. In celebration of the 2018 Illinois state bicentennial, the Cahokia Mounds were selected as one of the Illinois 200 Great Places by the American Institute of Architects Illinois component (AIA Illinois). It was recognized by USA Today Travel magazine, as one of the selections for 'Illinois 25 Must See Places'.

Development (9th and 10th centuries)


Although some evidence exists of occupation during the Late Archaic period (around 1200 BCE) in and around the site, 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. 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.

The city's complex construction of earthen mounds required digging, excavation and transportation by hand using woven baskets. Construction made use of 55 e6ft3 of earth, and much of the work was accomplished over 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.

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. 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.

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.

Rise and peak (11th and 12th centuries)
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, 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. Mississippian culture pottery and stone tools in the Cahokian style were found at the Silvernale site near Red Wing, Minnesota, and materials and trade goods from Pennsylvania, the Gulf Coast, and Lake Superior have been excavated at Cahokia.

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", an estimate that applies only to a 1.8 km2 high-density central occupation area. Studies of Cahokia's rise see large-scale immigration as an essential contributor to the city's initial rapid growth. Archaeologists estimate the city's population at between 6,000 and 40,000 at its peak, 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. 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. Its population may have been larger than contemporaneous London and Paris.

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.

Decline (13th and 14th centuries)
The population of Cahokia began to decline during the 13th century, and the site was abandoned by around 1350. Scholars have proposed environmental factors, such as environmental degradation through overhunting, deforestation and pollution, and climatic changes, such as increased flooding and droughts, 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.

Political, economic, or cultural problems may also have contributed to the community's decline. Thomas Emerson and Kristin Hedman argue that Cahokia's large immigrant population was a factor in the city's ultimate fragmentation, as differing languages, customs, and religions obstructed the creation of a cohesive Cahokian cultural identity. Analyses of Cahokian burial sites and the associated remains have also shown that many Cahokians were not native to the city or its immediate surrounding region. These immigrants were sometimes buried separately from native residents, a possible indicator of weak integration along ethnic lines. It is likely that social and environmental factors combined to produce the conditions that led people to leave Cahokia.

Another possible cause is invasion by outside peoples. Many theories since the late 20th century propose conquest-induced political collapse as the primary reason for Cahokia's abandonment. The only evidence of warfare found is defensive wooden stockade and watchtowers that enclosed Cahokia's main ceremonial precinct. However, the palisade may have been more for ritual or formal separation than for military purposes. As Cahokia's population shrank over the 13th century, Cahokia's palisade was rebuilt several times to encompass increasingly-smaller portions of the city.

Diseases transmitted among the large, dense urban population are another possible cause of decline. Similarly, health issues are known to arise through maize-intense diets like Cahokia's. Isotope analysis of burial remains at Cahokia has revealed iron-deficiency anemia and enamel defects potentially stemming from Cahokia's reliance on maize. However, evidence tying nutritional deficiencies to a broader societal collapse has not been conclusively identified.

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. 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, dikes, and levees that protected at least the central city throughout its inhabited history. In another indication of flood mitigation efforts, Cahokians dispersed their agricultural lands among both lowland and upland fields, thereby reducing the chances that a single cataclysmic flood would wipe out the city's food supply.

Archeologists discovered evidence in 2020 that there was a population rebound following Cahokia's population minimum in 1400, with the population reaching a population maximum in 1650 and then declining again in 1700.

Agriculture
Cahokia was surrounded by rich agricultural lands. The city has been traditionally thought to have been a maize-centric civilization, the crop having been introduced to the region around AD 900. While maize is often credited with enabling Cahokia's early population growth, more recent research has suggested that Cahokian diets were quite varied, especially in the city's early period of existence. Thomas Emerson and Kristin Hedman attribute the discovery of Cahokian individuals with low-maize diets to the existence of hunter-gatherer immigrant communities who had not yet adopted maize as a staple food source.

Residents of outlying areas relied heavily on maize for subsistence, while residents of Cahokia's city center enjoyed more diverse diets. One interpretation is that higher levels of maize consumption may be correlated with a lower social status among Cahokian residents.

The impact that Cahokian agriculture had on the environment, and its relationship to the city's ultimate collapse, is hotly debated. The depletion of farming soil surrounding Cahokia may have led to a decline in food resources that doomed the city. Jane Mt. Pleasant, however, argues that these models of Cahokia's soil longevity are flawed, because it is based on modern understandings of crop yields that assume the use of plows. Cahokians' exclusive use of hand tools was less damaging to the soil and thus may have maintained soil quality far longer than is typical today, making a rapid collapse of agricultural productivity in Cahokia less likely.

Notable features
The original site contained 120 earthen mounds over an area of 6 sqmi, of which 80 remain today. To achieve that, thousands of workers over decades moved more than an estimated 55 e6cuft of earth in woven baskets to create this network of mounds and community plazas. Monks Mound, for example, covers 14 acre, rises 100 ft, and was topped by a massive 5000 sqft building another 50 ft high.

Urban landscape
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.

To the south of Monks Mound is the Grand Plaza, a large area that covered roughly 50 acre and measured over 1600 ft in length by over 900 ft 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. 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.

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 ). The feature, named the Rattlesnake Causeway by archaeologists, was an elevated embankment about 18 m wide, roughly 800 m in length and varies in height from 0.5 m to almost 1.3 m as it traverses a low swampy area to the south of the Grand Plaza. 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. 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".

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. 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.

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 from end to end, while the entire city is 5 mi across from east to west.

Domestic architecture
Cahokian residential zones were arranged into carefully planned clusters around plazas and mounds. Specific delineations and functions have been hard to determine, but many of these clusters may have been designed to accommodate religious or ethnic segregations. Cahokia's neighborhoods possessed a standardized suite of building types, including steam baths, council houses, and temples.

Cahokian domestic structures were generally of pole-and-thatch construction and followed rectangular footprints. Wall trenches were often used instead of posts for building construction.

Alleen Betzenhauser and Timothy Pauketat argue that upwards of 20 percent of Cahokia's neighborhood structures did not serve domestic functions, but were rather intended to facilitate engagement with non-human spiritual beings as part of an animistic religion. These beings may have resided in the building itself or inhabited large marker posts, similar to the posts used to build the Cahokia Woodhenge. Betzenhauser and Pauketat compare their theorized Cahokian buildings to similar historical examples such as shaking tents or medicine lodges.

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 high, 951 ft long, 836 ft wide and covers 13.8 acre. It contains about 814000 cuyd of earth. 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.

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 long and 48 ft wide, and could have been as much as 50 ft high. It was about 5000 sqft.

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.

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, 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. 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."

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.

Copper workshop


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. 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.

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. 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.

Cahokia Woodhenge
The Cahokia Woodhenge was a series of large timber circles located roughly 850 m 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. 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. Detailed analytical work supported the hypothesis that the placement of these posts was by design, 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.

The post holes found by Wittry are an example of how soil retains the memory of organic materials that decayed in the soil from thousands of years ago. Many soils have a naturally acidic component that breaks down most organic material pretty quickly, but leaves behind dark discoloration in the soil. The original posts of Cahokia Woodhenge left behind this same discoloration, allowing researchers to easily identify the soil as having once contained wooden posts.

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. In 1985, a reconstruction of Woodhenge III was built with the posts being placed into the original excavated post positions. The circle, which has 48 posts in the circle and a 49th central post, has been used to investigate archaeoastronomy at Cahokia. 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.

Related mounds
Until the 19th century, a series of similar mounds was documented as existing in what is now the city of St. Louis, some 8 mi to the west of Cahokia. Most of these mounds were leveled during the development of St. Louis, and much of their material was reused in construction projects.

The lone survivor of these mounds is Sugarloaf Mound. Located on the west bank of the Mississippi, it marked the initial border between St. Louis and the once autonomous city of Carondelet.

One of the largest Mississippian sites is Kincaid Mounds State Historic Site, located in Massac and Polk counties in southern Illinois. It is 140 mi southeast of Cahokia, located in the floodplain of the Ohio River. With a total of 19 mounds at the complex, it is considered the fifth-largest Mississippian site in terms of the number of monuments. It is believed to have been a chiefdom, as an elite burial mound was among those found. The site is designated as a National Historic Landmark.

Cahokia Museum and Interpretive Center
The Cahokia Museum and Interpretive Center, which receives up to a million visitors a year, was designed by AAIC Inc. The building, which opened in 1989, received the Thomas H. Madigan Award, the St. Louis Construction News & Reviews Readers Choice Award, the Merit Award from the Metal Construction Association, and the Outstanding Achievement Award from the Brick Manufacturer Association.

Academia
Cahokia has long been a point of interest in the academic community. As early as the 1960s, universities across the Midwest have gone to the site to conduct research in fields ranging from geology to archaeology. One of the most prominent archaeological researchers of Cahokia is Timothy Pauketat. He has been writing about and researching Cahokia for the majority of his professional career. Other prominent Cahokia academics include Warren Wittry, who was instrumental in the recovery of Cahokia Woodhenge.

Designations
Cahokia Mounds was first protected by the state of Illinois in 1923 when its legislature authorized purchase of a state park. Later designation as a state historic site offered additional protection, but the site came under significant threat from the federal highway building program in the 1950s. The highway program reduced the site's integrity; however, it increased funding for emergency archeological investigations. These investigations became intensive, and today continue. They have resulted in the present understanding of the national and international significance of the site. The site was designated a National Historic Landmark on July 19, 1964, and listed on the National Register of Historic Places on October 15, 1966.

In 1982, UNESCO (the United Nations Educational, Scientific and Cultural Organization) designated the site a World Heritage Site. This is the only such self-contained site in Illinois and among 24 World Heritage Sites in the United States in 2009.

State Senator Evelyn M. Bowles wrote about the Cahokia Mounds site: "Through the years my friends and I made occasional Sunday afternoon trips to the Mounds. When I became the State Senator, it afforded me the opportunity to secure funds for the acquisition of additional acreage in which there are smaller Mounds. Many of these have contained additional artifacts."

The designation has helped protect the property and attract funds to conduct research on this significant civilization.