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Alternate Perceptions Magazine, August 2017

What is under Monk's Mound?

by: Dr. Greg Little

Portions of this article were previously published and are also from The Illustrated Encyclopedia of Native American Indian Mounds & Earthworks.

The Cahokia (Illinois) Mound complex is the largest single grouping of Native American mounds and certainly one of the most important mound sites in the country. The overwhelming centerpiece of the 2,200-acre park, which once contained 120 mounds, is known as "Monk's Mound." It is the largest earthen mound in America, standing at about 100-feet tall with a base covering nearly 15 acres. The “higher level” base of the massive mound is 955 feet by 775 feet, however, there is evidence that the actual base (on a lower elevation) may have been 1,050 feet by 965 feet. (By contrast, the Great Pyramid of Giza covers 13 acres.) It was once thought that it took the native cultures an astonishing 250 years to build the mound, but 2015 it became clear that the construction time was 20 years or less. In 1998 an intriguing mystery emerged at this mound, one that still remains completely unexplained.

From atop Monk's Mound one can see the skyline of downtown St. Louis. The site was the major power point of the Mississippian-era Mound Building culture from A.D. 600 to about 1250. Within the 6 square miles of the center city it is believed that between 10,000 to 50,000 people lived. The mounds constructed at Cahokia contained over 55 million cubic feet of earth, carried, according to archaeologists, basketload by basketload. The very center of the city focused on Monk's Mound and a 40-acre area surrounded by a massive, 2-mile long stockade fortress. Another 16 mounds were protected inside the stockade. The stockade was made from 20,000 one-foot thick logs standing 12 feet high. Every 70-feet along the stockade were protective bastions. It was an impressive city at its height. By around AD 1300, the site was abandoned for unknown reasons, however, a lack of wood, disease, or the collapse of the chiefdom have all been cited as possible reasons.

Excavations on the top of Monk's Mound revealed that an imposing 5000-square foot building once sat on its apex. The building was 105 feet long, 48 feet wide, and had walls 50 feet high. It is thought to have been the chief ruler's residence. The mound was built in a series of stages (generally believed to have been 14 distinct building periods each lasting about 18 years). The flat top of the truncated pyramid was enormous and in 1987 some 5,000 people gathered on it.

Archaeological work at different areas of Cahokia have found hundreds of burials, sacrificed victims, pottery, points, burial goods, and countless artifacts. But the biggest surprise came in 1998 from work performed by nonarchaeologists.

In the 1980's rain erosion began causing a slumping on the east and west sides of Monk's Mound and simple attempts to reduce the erosion and water seepage were repeatedly tried to no avail. In January 1998 a construction drilling team was brought in to make five drains into the base of the west side of the mound's base. While drilling the fifth hole, something unexpected was struck—stone—a lot of it. Stone that should not have been there.

The drill bit first hit stone at a depth of 140-feet (horizontally into the second terrace) and 45-feet below the surface of the second terrace. From his experience drilling through stone, the drill operator related that it appeared to be sandstone or limestone. He continued drilling until the drill bit broke. By then he had gone through 32-feet of stone. The $5000 drill bit and an electronic sensor attached to it remain inside the hole to this day. Initially it was thought that the stone was probably a layer of stones that might have served as a platform.

In 1999 ground-penetrating radar, magnetometry, and resistivity surveys were done on the mound. They determined that there was a large, rectangular stone structure in the mound. However, two other densely packed rectangular structures (probably made of stone) were also found. One was above the large chamber the drill had tried to enter and the other was below it. Two of these stone structures were described by the archaeological teams as “walls.” Archaeologist William Woods of Southern Illinois University stated that it was a "dramatic find, it's so unexpected that it never has entered your mind before." Woods continued, "Stone does not occur naturally at Cahokia so any stone would have had to be brought by humans. Stone is uncommon at excavations there."

The explanation for the three stone structures at Monk's Mound likely relates to the finding that the mound was built in stages. It is probable that each of these three chambers are large burial crypts that were made after an important ruler died. After each chamber was constructed and burial ceremonies were performed, the mound was enlarged and heightened thereby covering the chamber. However, this was more characteristic of the earlier Adena and Hopewell cultures—but we'll perhaps never know. America archaeology laws and the lack of adequate funding will keep the mystery intact. But the size of these chambers and their undisturbed state would indicate that within them could be the greatest archaeological treasures in North America. And with those "treasures" there would be a lot of answers found to the many enigmas of America's Mound Builders.


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