Cahokia was Mississippian urban center that thrived for 500 years (A.D. 700-1500) and consisted of 120 earthen mounds in a six square mile area with a population of 20,000 -100,000 people. Cahokia was a principle trade center in the American Bottoms and influenced people from today's Red Wing, Minnesota  down to New Orleans, Louisiana.

The earliest French explorers, Joliet and Marquette (1673), Tonti (1680), La Salle (1682) identified Mississippian mounds near St. Louis, Cahokia and Kaskaskia but somehow leave out the center of Cahokia. George Rogers Clark as early as 1778 and Gen, George Collot, 1796 identify other sites in the area along a road from Kaskaskia, IL to St. Louis, MO but ignore the huge mounds at Cahokia. In 1809 a Nicholas Jarrot donated the area to Trappist monks who lived on some of the mounds of the Cahokia area. As a result the largest mound at Cahokia has been called 'Monks Mound'. After the Trappist Monks  left the area was owned by a T. Hill who actually lived on the top of Monks Mound in 1830 and was buried on the top of the mound. From 1866-1925 Thomas Ramey owned the property. During this time many of the 20 -30 of the original mounds were destroyed or even leveled. Early sketches indicates this and give a clue to the shape of the original mounds. In 1834-35 Featherstonhaugh visited the site and published a drawing in 1844.

In the 1880s W. McAdams, a local amateur, conducted excavations and generated a number of reports. Another local, J. F. Snyder promoted preservation of Cahokia and Dr. A. J. Patrick made the first accurate maps of the site in the 1890s .

In 1921 Warren K. Morehead and M. M. Leighton conducted the first official archaeological investigation and demonstrated the mounds were manmade. This premise had been contested in the 19th century due to the bias of many based on racism and justification for destruction of the many mounds in the area.

Cahokia represents a Mississippian city located in the American Bottoms that was built and occupied between A.D. 800-1400. It is one of at least five Mississippian city/complexes in the area at the same time. The Cahokia sites consist of a main wood palisaded area encompassing a plaza of about a dozen earth works to include truncated mounds, conical mounds and tombs.The main 'Monks Mound' was built in three to five stages and has an unusual three-four terraced construction. This mound is 100 ft. high and 819,230 sq. ft. at the base. The entire city, including more than 120 mounds, is 3,700 sq. acres or 5.8 sq. miles. Architecture and layout of the city involves archaeoastronomical alignment, religious, trade, transportation and defense considerations. Recent excavation of Mound 72 has revealed 272  burials. Two individuals were buried between a layer of 20,000 beads with special bird image tablets, chunky game stones and multiple caches of arrow points.

Some of the burials ( skeletal material and other artifacts) appear to be ritualistic in nature and were meant to accompany the two prominent individuals in the center with all of the elaborate grave goods. This kind of burial indicates a social hierarchy observed by Du Pratz and La Petit in the 1700's and suggests the presence of the Sun nobility at Cahokia.

Another feature at Cahokia were a number of circular wooden structures used as analog calculators for astronomical measurements. These were built to the west of the great pyramid and consisted of circles with tree sized posts (painted red) (12-72) to mark line of site azimuths with the main mound at auspicious times such as the winter and summer solstice in conjunction with other celestial bodies rising and setting. They are named Woodhenge after Stonehenge in England's Avebury Plain. Even more confusing is the fact that Woodhenge structures have been discovered near Stonehenge. The ones at Cahokia were using the man-made structures as horizonal markers, rather than the natural terrain. There may have been observational platforms erected in the center of the circles.

Finally in addition to these many activities going on at Cahokia there needed to be intensive CBS agriculture to support the people and elaborate trade networks boosting the economy. During its peak from A.D. 950-1200 Cahokia was using the American Bottoms and Mississippi River as a centralized trade network of market economies, reciprocal networks and redistribution networks.

Cahokia has take a considerable amount of abuse since its abandonment 500 years ago. Some of the mounds were eradicated and many of the adjacent cities were leveled, especially in St. Louis, MO. Some of the Cahokia area was purchased by the State of Illinois in 1925 as the Cahokia Mounds State Historic Site. Today Cahokia is managed by the Illinois Preservation Agency. In 1982, Cahokia Mounds were added to UNESCO as a World Heritage Site.