The Cahokia Mounds, also called Cahokia, is the location of a Native American city that existed from about 1050 to 1350 CE. This city was located directly across the Mississippi River from present-day St. Louis. The Cahokia Mounds State Archaeology Park is in south-western Illinois, between East St. Louis and Collinsville. The park covers 2,200 acres, or about 3.5 square miles, and includes around 80 manmade mounds. However, the ancient city was much larger. At its peak around 1100 CE, the city covered about 6 square miles, had about 120 large structures of different sizes and purposes, and had a population of between 15,000 and 20,000 people.

Cahokia was the largest and most important city of the Mississippian culture, which created advanced societies across much of what is now the Central and Southeastern United States, starting around 1000 CE. Today, the Cahokia Mounds are considered the largest and most complex archaeological site in the United States north of the ancient cities in Mexico.

The original name of the city is unknown. The mounds were later named after the Cahokia tribe, a group of Illiniwek people who lived in the area when French explorers arrived in the 17th century. This was long after the city was abandoned, so the Cahokia tribe was likely not related to the earlier Mississippian people. It is likely that several different groups of Native Americans lived in the area during the city’s peak.

The Cahokia Mounds are a National Historic Landmark and protected by the state. It is also one of 26 UNESCO World Heritage Sites in the United States. The site is the largest pre-Columbian earthwork north of Mexico in the Americas. It is open to the public and managed by the Illinois Historic Preservation Division with support from the Cahokia Mounds Museum Society. In 2018, the Cahokia Mounds were chosen as one of the Illinois 200 Great Places by the American Institute of Architects Illinois component. They were also listed as one of the "Illinois 25 Must See Places" by USA Today Travel magazine.

History

Cahokia, as it is known today, was first settled around 600 CE during the Late Woodland period. Evidence of earlier occupation exists from the Late Archaic period (around 1200 BCE), but the area as defined by modern archaeologists became a permanent settlement later. Mound building at Cahokia began during the Mississippian cultural period, around the 9th century CE. The people who lived there did not leave written records beyond symbols carved on pottery, shells, copper, wood, and stone. However, the planned layout of the community, the construction of woodhenge, mounds, and burial sites show that Cahokia was home to a complex and sophisticated society.

Cahokia became the most important center of the Mississippian culture, which spread across the Midwest, Eastern, and Southeastern United States. Its location near the confluence of the Mississippi, Missouri, and Illinois Rivers made it a key trading hub. People in Cahokia traded with communities as far north as the Great Lakes and as far south as the Gulf Coast. Items exchanged included copper, Mill Creek chert, shark teeth, and lightning whelk shells.

Before 1000 CE, people in the American Bottom region lived in small settlements of 50 to 100 people that were occupied for only 5 to 10 years. At least two larger clusters of settlements existed in Cahokia, one from the mid-7th to 9th centuries. Later, these settlements were organized based on cardinal directions and social groups. By the end of the 10th century, many of these small settlements merged into larger villages that included central posts, pits, and structures arranged in specific patterns.

A large, nucleated community covering 35–70 hectares (86–173 acres) began forming in Cahokia around the late 900s CE. At this time, a few thousand people lived in the American Bottom region. Mound building occurred in Cahokia and at a nearby site near Horseshoe Lake. The people here were farmers, but maize was not yet a major crop. Maize became important around 900 CE, while most crops grown earlier came from the Eastern Agricultural Complex, an older farming tradition.

Around 1050 CE, Cahokia experienced rapid growth, often called the "Big Bang." Three urban areas—St. Louis, East St. Louis, and Cahokia—were established during this time. A city grid aligned to the north was built around the Grand Plaza, Rattlesnake Causeway, and mounds. This grid replaced earlier Woodland settlements, and material culture, such as pottery and architecture, became more uniform. Mound construction expanded across the region, including the uplands to the east. Some mounds were built on former settlement sites, possibly to highlight ancestral connections in the new social order. Villages either grew into mound centers or became small farms or single households. New settlement types, such as nucleated villages, mound centers, and dispersed clusters, appeared throughout the region.

Building the mounds required digging, transporting, and shaping large amounts of earth by hand using woven baskets. Over decades, 55 million cubic feet (1.6 million cubic meters) of earth were used to create the mounds. The city’s large, flat ceremonial plazas, surrounded by mounds and connected by pathways and courtyards, suggest Cahokia was a central religious and pilgrimage site.

At its peak, Cahokia was the largest city north of Mesoamerica. Its population grew rapidly after 1050 CE. By 1100 CE, the population in the central area increased from 1,400 to 2,800 people to between 10,200 and 15,300 people. Later discoveries of residential areas to the west of Cahokia led archaeologists to estimate the city’s population at between 6,000 and 40,000 at its height. If the highest estimates are correct, Cahokia was larger than any U.S. city until the 1780s, when Philadelphia’s population exceeded 40,000.

Cahokia’s growth was partly due to large-scale immigration. Non-local ceramics found in the area suggest people moved to Cahokia from regions like the lower Ohio Drainage, Lower Mississippi Valley, Upper Midwest, and south-central plains. These immigrants settled in villages in the eastern uplands, known as the Richland Complex, where farming and textile production occurred. These practices may have been ways to support the central city. One example is the mound-and-plaza pairing, which was adopted from the Coles Creek culture.

Between 1050 and 1150 CE, Cahokia had strong trade connections across the mid-continent and possibly beyond. Mill Creek chert from southwestern Illinois was used to make farming tools, which were in high demand. Cahokia controlled the distribution of these tools, not their production, which helped establish a new agricultural system. Cahokian-style pottery and tools were found in Minnesota, and materials from Pennsylvania, the Gulf Coast, and Lake Superior were discovered in Cahokia. People also traveled to Mississippi and Wisconsin, where they built settlements and mounds.

During the Stirling phase (1100–1200 CE), Cahokia reached its peak in political centralization. Religion played a key role in maintaining political power. The Emerald Acropolis mound in the uplands was aligned with lunar cycles and was associated with the moon, water, femininity, and fertility. Immigrants were drawn to Cahokia as pilgrims, attracted by its religious significance. Political control in the surrounding areas was managed through temple complexes with T- or L-shaped structures and sweatlodges. Rituals involving tobacco, red cedar, agricultural produce, and female figurines made of flint clay were practiced there. Public rituals, such as the sacrifice of women at mounds, were also recorded.

Contemporary usage (post 19th-century)

Cahokia is one of the most important cities in the history of North America. Its influence has been far-reaching, and many Native American groups and tribes today see the site as a key part of their heritage. The Osage Nation works closely with archaeologists and site managers to preserve the area. One of the few remaining Mississippian mounds near St. Louis, called Sugarloaf Mound, was bought by the Osage Nation to protect it for future generations.

Many Indigenous groups, including the Cherokee, Choctaw, Chickasaw, and Muscogee-Creek, continue traditions similar to those of Cahokia, such as building mounds. Native American people still regard the site as sacred and visit it to perform ceremonies and dances. The site has also inspired Native American art. Howard Revard, an Osage Nation poet, wrote about Cahokia in his book Winning the Dust Bowl. Jaune Quick-to-See Smith, an artist from the Confederated Salish and Kootenai Tribes, created artworks like State Names Map: Cahokia and Trade Canoe: Cahokia, which were displayed at the St. Louis Art Museum.

The Cahokia Museum and Interpretive Center, which receives up to one million visitors each year, was designed by AAIC Inc. The building opened in 1989 and has won several awards, including 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.

Cahokia has been a major focus for academic research since the 1960s. Universities in the Midwest have studied the site in fields such as geology and archaeology. Timothy Pauketat is one of the most well-known researchers who has studied Cahokia throughout his career. Warren Wittry played a key role in recovering Cahokia Woodhenge.

Cahokia Mounds was first protected by the state of Illinois in 1923 when the legislature approved the purchase of a state park. Later, it was designated a state historic site, which added more protection. However, in the 1950s, the federal highway building program threatened the site. While the highway program damaged the site’s integrity, it also increased funding for urgent archaeological studies. These studies continue today and have helped people understand the site’s national and international importance. The site was named a National Historic Landmark on July 19, 1964, and added to the National Register of Historic Places on October 15, 1966.

In 1982, UNESCO (the United Nations Educational, Scientific, and Cultural Organization) declared Cahokia a World Heritage Site. This is the only self-contained World Heritage Site in Illinois and one of 24 in the United States in 2009.

State Senator Evelyn M. Bowles wrote about Cahokia Mounds:
“The designation has helped protect the property and attract funds to conduct research on this significant civilization.”

Agriculture

Cahokia was located near fertile farmland. The city was long believed to be focused on growing maize, a crop that arrived in the region around AD 900. Although maize is often seen as a key reason for Cahokia's population growth, recent studies suggest that early Cahokian diets included many different foods. Crops such as goosefoot and sumpweed from the Eastern Agricultural Complex were also grown and eaten. Thomas Emerson and Kristin Hedman believe that some Cahokian individuals had diets with little maize because they were part of immigrant groups who still relied on hunting and gathering rather than farming maize.

People living in areas outside Cahokia’s city center depended heavily on maize for food. In contrast, people in the city center had more varied diets. One idea is that eating more maize might have been linked to lower social status among Cahokians.

The effects of Cahokian farming on the environment and its role in the city’s decline are debated. Some believe that overuse of soil near Cahokia reduced food supplies, leading to the city’s downfall. However, Jane Mt. Pleasant argues that these ideas are based on modern farming practices, such as using plows, which Cahokians did not use. Instead, Cahokians used hand tools, which caused less harm to the soil and may have kept it fertile for longer, making a sudden drop in food production less likely.

Historian Daniel Richter notes that Cahokia’s greatest growth happened during the Medieval Warming Period. This time likely helped spread farming techniques, such as growing maize, beans, and gourds, which were adapted to northern climates from their origins in Mesoamerica. Richter also points out that Cahokia’s development happened at the same time as the Chaco Canyon society in the Southwest, which also built large structures in a society with social classes. Cahokia’s decline happened during the Little Ice Age, though by then, the farming of maize, beans, and gourds was already well established across temperate North America.

Notable features

The original site had 120 earthen mounds spread over an area of 6 square miles (16 km²), and 80 of these mounds remain today. To create this, thousands of workers moved more than 55 million cubic feet (1,600,000 m³) of earth in woven baskets over many years. These efforts formed a network of mounds and community plazas. For example, Monks Mound covers 14 acres (5.7 ha), rises 100 feet (30 m), and had a massive building on top that was 5,000 feet (460 m) long and 50 feet (15 m) high.

Early in Cahokia’s history, the city experienced a major construction boom. Along with the first phase of Monks Mound, an organized urban layout was created. This layout was based on a symbolic four-part worldview and was aligned with the four cardinal directions. The main east-west and north-south paths were centered around Monks Mound. Four large plazas were built to the east, west, north, and south of Monks Mound.

To the south of Monks Mound is the Grand Plaza, a large area covering about 50 acres (20 ha) and measuring over 1,600 feet (490 m) in length and over 900 feet (270 m) in width. At first, researchers thought the flat, open area reflected Cahokia’s location on the Mississippi River’s floodplain. However, soil studies showed the landscape was originally a series of ridges and swales. The city’s people deliberately leveled and filled the area, creating a flat surface. This was part of the city’s advanced engineering. The Grand Plaza was used for large ceremonies, gatherings, and games like chunkey. In chunkey, players rolled a disc-shaped stone across the field and threw spears where they thought the stone would land. The game required careful judgment and aim.

A major ceremonial north-south path connects the main area of Cahokia to a large mortuary mound to the south, now called Rattlesnake Mound (Mound 66). This path, called the Rattlesnake Causeway by archaeologists, was an elevated embankment about 18 meters (59 feet) wide, 800 meters (2,600 feet) long, and varied in height from 0.5 meters (1.6 feet) to 1.3 meters (4.3 feet). It crossed a swampy area and was aligned 5 degrees east of north. This direction is thought to mirror the maximum southern rise of the moon, which was 5 degrees west of north. This alignment may have had symbolic meaning related to Cahokia’s lunar maize goddess of the underworld. The causeway’s connection to Mound 72, the swampy area it crossed, and its endpoint at Rattlesnake Mound suggests it may have been seen as a "Path of Souls."

The central area of Cahokia was surrounded by a 2-mile-long (3.2 km) palisade with protective bastions. This was added later and cut through some existing neighborhoods. Evidence of the palisade was found during excavations, and it appears the structure was rebuilt multiple times. Its design shows it was built mainly for defense.

Beyond Monks Mound, up to 120 additional mounds were located at varying distances from the city center. So far, 109 mounds have been identified, with 68 of them in the park area. These mounds are divided into three types: platform, conical, and ridge-top. Each type likely had its own purpose. The city center was arranged in a diamond shape, about 1 mile (1.6 km) from end to end, and the entire city stretched 5 miles (8 km) from east to west.

Cahokian residential areas were organized into planned clusters around plazas and mounds. While the exact functions of these clusters are unclear, some may have been used for religious or ethnic groups. The neighborhoods had standardized building types, including steam baths, council houses, and temples.

Most Cahokian homes were built with wooden poles and thatched roofs, following rectangular shapes. Wall trenches were often used instead of posts for construction.

Alleen Betzenhauser and Timothy Pauketat suggest that up to 20 percent of Cahokia’s neighborhood buildings were not used for daily living but instead for spiritual purposes. These buildings may have been used to interact with non-human spiritual beings, similar to the posts used in the Cahokia Woodhenge. They compare these buildings to structures like shaking tents or medicine lodges.

Monks Mound is the largest structure in Cahokia and the city’s central focus. It is a massive platform mound with four terraces, 10 stories tall, and is the largest man-made earthen mound north of Mexico

Greater Cahokia

Cahokia is known as one of the main locations in a group of many places that include East St. Louis, St. Louis Mounds, Janey B. Goode, and the Mitchell site. This area is called "Greater Cahokia" because all these places were connected and worked together.

Related mounds

Before the 1900s, people recorded a group of similar mounds in what is now the city of St. Louis, about 8 miles (13 kilometers) west of Cahokia. Most of these mounds were flattened when St. Louis grew, and much of their material was reused in construction projects.

One remaining mound from this group is Sugarloaf Mound. It was on the west side of the Mississippi River and showed where St. Louis and the old city of Carondelet met. A small part of another related mound is found in O'Fallon Park in St. Louis.

Kincaid Mounds State Historic Site is one of the largest Mississippian sites. It is located in Massac and Polk counties in southern Illinois, 140 miles (230 kilometers) southeast of Cahokia, in the floodplain of the Ohio River. The site has 19 mounds, making it the fifth-largest Mississippian site by the number of monuments. It is believed to have been a chiefdom, as an elite burial mound was found there. The site is recognized as a National Historic Landmark.

• A priest from the Mississippian culture in the 1200s, in Cahokia, holding a ceremonial flint mace and a head used in a ritual
• Tamarois et Caouquias on a French map of Illinois from 1718, south of where the Illinois and Mississippi rivers meet (modern area shown) from Carte de la Louisiane et du Cours du Mississipi by Guillaume de L'Isle
• The Rattlesnake Causeway connects Monks Mound to Mound 66 and was the main ceremonial path going north and south
• The "Chunkey Player" statuette, made of Missouri flint clay, shows the ancient Native American game of chunkey. It was found at a Mississippian site in Muskogee County, Oklahoma, showing how far the trade network of this culture extended
• Clay statuette found at the Cahokia site
• Incised sandstone tablet of a Birdman discovered in 1971 during digging on the east side of Monks Mound