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 directly across the Mississippi River from present-day St. Louis. The Cahokia Mounds State Archaeology Park is located in south-western Illinois, between East St. Louis and Collinsville. The park covers 2,200 acres (890 hectares), or about 3.5 square miles (9 square kilometers), 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 (16 square kilometers), had about 120 earthworks of different sizes, shapes, and purposes, and was home to 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 north of the major pre-Columbian 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 not necessarily related to the people who lived there during the city's peak. It is likely that several different groups of Native Americans lived in the Cahokia Mounds area during the city's time.

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

History

Cahokia, as it is known today, was first settled around 600 CE during the Late Woodland period. Evidence of earlier occupation from the Late Archaic period (around 1200 BCE) exists in and around the site. 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, but symbols on pottery, marine shell, copper, wood, and stone provide clues about their society. Later evidence, such as planned communities, woodhenge structures, mounds, and burial sites, shows that Cahokia was a complex and advanced society.

Cahokia became the most important center of the Mississippian culture, which spread across major waterways in what is now 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. 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, populations in the American Bottom lived in small settlements of 50 to 100 people, used for short periods of 5–10 years. At least two larger clusters existed at Cahokia, one from the mid-7th to 9th centuries. Later, settlements were organized based on cardinal directions and social groups. By the end of the 10th century, many settlements merged into larger villages that included central posts, pits, and structures.

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 site near Horseshoe Lake to the north. These Late Woodland people were farmers, but maize was not yet a major crop. Maize became important around 900 CE, while earlier crops came from the Eastern Agricultural Complex, an older farming tradition.

Around 1050 CE, Cahokia experienced rapid growth, known as the "Big Bang." Three urban areas—St. Louis, East St. Louis, and Cahokia—were built during this time. A planned city grid, aligned with the Grand Plaza, Rattlesnake Causeway, and mounds, replaced earlier settlements. Material culture, such as pottery and architecture, became more uniform across the region. Mound construction expanded in the 11th century, both in the floodplain and in the uplands to the east. Some mounds were built on earlier settlement sites, possibly to highlight ancestral connections. Villages either grew into mound centers or became small farms or households. New settlement types, such as nucleated villages, mound centers, and single-family homes, appeared.

The construction of Cahokia’s mounds required digging, moving, and placing earth by hand using woven baskets. Over decades, 55 million cubic feet (1.6 million cubic meters) of earth were used to build the mounds. Large, flat ceremonial plazas surrounded the mounds, with homes for thousands connected by pathways and courtyards. This suggests Cahokia was a central religious pilgrimage site.

At its peak, Cahokia was the largest urban center north of Mesoamerican cities in Mexico and Central America. Its population grew rapidly after 1050 CE. A 2007 study estimated that between 1050 and 1100 CE, Cahokia’s population increased from 1,400 to 2,800 people to 10,200 to 15,300 people in a 1.8-square-kilometer (0.69-square-mile) central area. Later excavations found additional residential areas to the west, leading to estimates of 6,000 to 40,000 people at its peak. If the highest estimates are correct, Cahokia was larger than any U.S. city until the 1780s when Philadelphia’s population exceeded 40,000. Its 12th-century population may have been larger than that of London or Paris at the time.

Cahokia’s growth was driven by large-scale immigration. Non-local ceramics found at the site suggest interaction with groups from the lower Ohio Drainage (Yankeetown), Lower Mississippi Valley (Coles Creek), Upper Midwest, and south-central plains (Caddo). Immigrants settled in the Richland Complex, where intensive farming and textile production occurred. These practices may have supported the central city. The Coles Creek tradition influenced Cahokia’s use of mounds and plazas.

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. Cahokian-style pottery and tools were found at sites like Silvernale in Minnesota, while materials from Pennsylvania, the Gulf Coast, and Lake Superior were discovered at Cahokia. Cahokians also built settlements at the Carson site in Mississippi and a religious center at Trempleau Bluffs in Wisconsin.

During the Stirling phase (1100–1200 CE), Cahokia reached its height of political centralization. Religion played a key role in maintaining political power. The Emerald Acropolis mound in the uplands was associated with lunar cycles, water, femininity, and fertility. Immigrants were drawn to Cahokia as pilgrims. Political control extended to temple complexes with T- or L-shaped structures and sweatlodges. Rituals involving tobacco, red cedar, agricultural products, and female figurines were practiced there. Public rituals, such as the sacrifice of women at mounds, were also documented.

Contemporary usage (post 19th-century)

Cahokia is one of the most important cities in the history of North America. Its influence has reached many areas. Many Native American tribes today see the site as important to their history. The Osage Nation works closely with archaeologists and those who manage the site. One of the few remaining Mississippian mounds near St. Louis, called Sugarloaf Mound, was bought by the Osage Nation to protect it for the future.

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 consider the site sacred and visit it to perform ceremonies and dances. The site has inspired many Native American artists. Howard Revard, a well-known poet from the Osage Nation, wrote about Cahokia in his book Winning the Dust Bowl. Artist Jaune Quick-to-See Smith, from the Confederated Salish and Kootenai Tribes, created artworks titled "State Names Map: Cahokia" and "Trade Canoe: Cahokia" based on the site. These works were shown at the St. Louis Art Museum.

The Cahokia Museum and Interpretive Center, which gets up to a million visitors each year, was designed by AAIC Inc. The building, opened in 1989, 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 focus for scholars for many years. Starting in the 1960s, universities in the Midwest have visited the site to study subjects like geology and archaeology. Timothy Pauketat is one of the most well-known researchers who has studied Cahokia for most of his career. Warren Wittry helped find and preserve Cahokia Woodhenge.

Cahokia Mounds was first protected by the state of Illinois in 1923 when the state bought land to create a park. Later, it was declared a state historic site, which gave it more protection. However, in the 1950s, plans for a federal highway system threatened the site. Although the highway project damaged parts of the site, it also led to more funding for urgent archaeological studies. These studies continue today and have helped people understand the site’s importance. In 1964, Cahokia was named a National Historic Landmark, and in 1966, it was added to the National Register of Historic Places.

In 1982, UNESCO, the United Nations Educational, Scientific and Cultural Organization, named Cahokia a World Heritage Site. This is the only such site in Illinois and one of 24 in the United States at that time.

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. People have long believed that Cahokia’s society focused heavily on growing maize, a crop that arrived in the area around AD 900. While maize is often seen as the reason Cahokia’s population grew quickly, newer research suggests that early Cahokians ate a wide variety of foods. Crops like goosefoot and sumpweed, which were part of the Eastern Agricultural Complex, were also grown and consumed. Thomas Emerson and Kristin Hedman explain that some Cahokians ate little maize because they were immigrants who still relied on hunting and gathering instead of farming maize.

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

Scholars debate how Cahokian farming affected the environment and whether it caused the city’s decline. Some believe that overuse of farmland may have led to poor soil quality, reducing food supplies and harming the city. However, Jane Mt. Pleasant argues that these ideas are incorrect because they assume Cahokians used plows, which damage soil. Instead, Cahokians used hand tools, which caused less harm to the soil and may have kept it productive for longer.

Historian Daniel Richter notes that Cahokia’s greatest growth happened during the Medieval Warming Period. This time brought better farming conditions in northern North America, allowing people to grow maize, beans (a type of legume), and gourds (a type of squash). These crops were adapted from Mesoamerica to fit the cooler northern climate. 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 different social classes. Cahokia’s decline happened during the Little Ice Age, though by then, the three main crops were already well-established across temperate North America.

Notable features

The original site had 120 earthen mounds spread across 6 square miles (16 km²), and 80 of these mounds remain today. To build this, thousands of workers moved more than 55 million cubic feet (1,600,000 m³) of earth in woven baskets over many years to create 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 large building on top that was 5,000 feet (460 m) long and 50 feet (15 m) high.

Early in its history, Cahokia had a major construction period. Along with the first stage of Monks Mound, the city was planned with a layout that reflected a symbolic worldview divided into four parts, aligned with the four directions. The main east-west and north-south paths were centered around Monks Mound, and four large plazas were built to the east, west, north, and south of it.

To the south of Monks Mound is the Grand Plaza, a large open area covering about 50 acres (20 ha) and measuring over 1,600 feet (490 m) long by 900 feet (270 m) wide. Researchers first thought the flat area was natural because of the river’s floodplain, but soil studies showed the land was originally ridges and valleys. The city’s people intentionally leveled and filled the area, showing advanced engineering skills. The Grand Plaza was used for ceremonies, gatherings, and games like chunkey, where players rolled a disc-shaped stone and threw spears where they thought the stone would land.

A major ceremonial path, the north-south axis, connects the central area of Cahokia to a large burial mound called Rattlesnake Mound (Mound 66) to the south. This path, called the Rattlesnake Causeway by archaeologists, was an elevated walkway about 59 feet (18 meters) wide and 2,600 feet (800 meters) long. It was built over a swampy area and aligned 5° east of north, possibly to mirror the moon’s path. This alignment may have had symbolic meaning related to the city’s beliefs about a lunar goddess connected to the underworld. The causeway’s location near Mound 72, the swampy area it crossed, and its end at Rattlesnake Mound suggests it was seen as a "Path of Souls."

The central area of Cahokia was protected by a 2-mile-long (3.2 km) wooden wall with defensive towers. This wall, added later, cut through some existing neighborhoods. Archaeologists found evidence of the wall during excavations and noted it was rebuilt multiple times. The towers suggest the wall was built for defense.

Beyond Monks Mound, as many as 120 additional mounds were located at different distances from the city center. So far, 109 mounds have been found, with 68 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 shaped like a diamond, about 1 mile (1.6 km) from end to end, and the entire city stretched 5 miles (8 km) from east to west.

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

Most homes in Cahokia were built with wooden poles and thatched roofs, following rectangular shapes. Sometimes, trenches were used instead of posts for construction.

Alleen Betzenhauser and Timothy Pauketat suggest that up to 20% of Cahokia’s neighborhood buildings were not homes but were used to interact with spiritual beings as part of an animistic religion. These buildings may have housed spirits or had large posts similar to those in the Cahokia Woodhenge. They compare these structures to historical examples like shaking tents or medicine lodges.

Monks Mound is the largest structure in Cahokia and the central part of the city. It is a massive platform mound with four terraces, 10 stories tall, and is the largest man-made earthen mound north of Mexico. Facing south, it is 100 feet (30 m) high, 951 feet (290 m) long, 836 feet (255 m) wide, and covers 13.8 acres (5.6 ha). It contains about 814,000 cubic yards (622,000 m³) of earth. The mound was built over several centuries in up to 10 stages, growing taller and wider as terraces and aprons were added.

Monks Mound was named after Trappist monks who briefly lived there after European settlers arrived. Excavations on top of the mound revealed a large building, likely a temple or the home of a chief, which could have been seen from across the city. This building was about 105 feet (32 m) long, 48 feet (15 m) wide, and up to 50 feet (15 m) high. It was located on top of Monks Mound.

In August 2007, the east and northwest sides of Monks Mound were excavated to prevent erosion. These areas were later repaired to protect the mound.

During excavations of Mound 72, a ridge-top burial mound south of the city, archaeologists found the remains of about 270 people, including paired male and female burials. One burial, called the Beaded Burial or Birdman, was placed on a bed of 10,000 marine-shell beads arranged in the shape of a falcon. The falcon’s head was near the man’s head, and its wings and tail were under his arms and legs. Other burials in the mound had exotic materials and large numbers of shell beads.

The falcon warrior, or "birdman," is a common symbol in Mississippian culture. This burial had strong symbolic meaning. Nearby, a cache of finely made arrowheads of different styles and materials was found, showing Cahokia’s trade connections across North America.

Archaeologists found over 250 skeletons in Mound 72. Scholars believe about 62% of these were sacrificial victims, based on signs of ritual execution, burial methods, and other evidence. These included:

• Four young males missing their hands and

Greater Cahokia

Cahokia is a major area with many closely spaced sites, including East St. Louis, St. Louis Mounds, Janey B. Goode, and the Mitchell site. This area is often called "Greater Cahokia" because all the sites were connected to each other.

Related mounds

Until the 19th century, a group of similar mounds was recorded as being in what is now the city of St. Louis, about 8 miles (13 kilometers) west of Cahokia. Most of these mounds were flattened during the growth of St. Louis, and much of their material was used again in building projects.

One remaining example of these mounds is Sugarloaf Mound. It is located on the west side of the Mississippi River and marked the original border between St. Louis and the once-independent city of Carondelet. A part of the base of another mound, likely connected to these, is found in O'Fallon Park in St. Louis.

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

• A Mississippian-era priest from the 13th century, standing in Cahokia’s city center, holding a ceremonial flint mace and a severed head used in rituals
• Tamarois et Caouquias, shown on a French map of Illinois from 1718, located south of where the Illinois and Mississippi rivers meet (modern area highlighted) from Carte de la Louisiane et du Cours du Mississipi by Guillaume de L'Isle
• The Rattlesnake Causeway, a path connecting Monks Mound to Mound 66, served as the city’s main north-south route for ceremonies
• A small statue called the "Chunkey Player," made from Missouri flint clay, represents the ancient Native American game of chunkey. The statue was likely created near Cahokia Mounds and was found at a Mississippian site in Muskogee County, Oklahoma, showing the wide reach of this culture’s trade network
• A clay statue discovered at the Cahokia site
• A carved sandstone tablet showing a Birdman, found in 1971 during digging on the east side of Monks Mound