Cahokia Mounds is the site of the largest prehistoric Indian city north of Mexico. At its height, the city, arranged around open plazas, had approximately 20,000 residents. A great wooden stockade encircled the Central Ceremonial Precinct. A total of 120 mounds were built in the area, as well as several Woodhenges, used as solar calendars.

The 2200-acre State Historic Site includes an interpretive center and 70 mounds, which were built by the city’s prehistoric inhabitants.

"Monks, Mounds and the Lewis and Clark Connection"

Although Lewis and Clark never visited Cahokia Mounds, there are some connections with the site.

While at Camp Du Bois in the winter of 1803-04, Clark and another member of the group did visit some mounds to the east of the camp and recorded this in the journals. Today, this site is called the Grassy Lake site by archaeologists, and it was once composed of 11 mounds along the edge of a terrace overlooking the floodplain on the south edge of South Roxanna. Only one mound survives today in Dad’s Park.

The other connection was actually after the expedition. While on their journey west, at the Mandan village in North Dakota, Lewis and Clark hired Toussaint Charbonneau to serve as an interpreter, and he was accompanied by his wife, Sacagawea and their newly born son, Jean Baptiste Charbonneau. After the expedition, William Clark persuaded Toussaint and Sacagawea to let him educate their son in St. Louis, to which they agreed. In the fall of 1809, they were finally able to bring him to St. Louis. Although Clark was out of town, Jean Baptiste was baptized in St. Louis on Dec. 29, 1809. The priest who performed the baptism was Dom Urbain Guillet, leader of the colony of Trappist Monks who had recently settled at Cahokia Mounds. Previously, Guillet had consulted Meriwether Lewis, who was territorial governor, about possibly getting some federal land grant in Missouri for their colony, but they later decided to settle at Cahokia Mounds (then known as Cantine Mounds) in Illinois.