Artist's conception of Woodhenge III at sunrise circa 1000 CE
|Location||Collinsville, Illinois, United States|
|Region||Madison County, Illinois|
|Cultures||Middle Mississippian culture|
|Archaeologists||Warren Wittry, Robert L. Hall, William R. Iseminger|
|Architectural styles||timber circle|
|Architectural details||Number of monuments: 1 Number of temples:|
The Cahokia Woodhenge was a series of large timber circles located roughly 850 metres (2,790 ft) to the west of Monks Mound at the Mississippian culture Cahokia archaeological site near Collinsville, Illinois. They are thought to have been constructed between 900 and 1100 CE; with each one being larger and having more posts than its predecessor. The site was discovered as part of salvage archaeology in the early 1960s interstate highway construction boom and one of the circles was reconstructed in the 1980s. The circle has been used to investigate archaeoastronomy at Cahokia. Annual equinox and solstice sunrise observation events are held at the site.
Discovery and excavation
The existence of the series of woodhenges at Cahokia was discovered during salvage archaeology undertaken by Dr. Warren Wittry in the early 1960s in preparation for a proposed highway interchange. Although the majority of the site contained village house features, a number of unusually shaped large post holes were also discovered. The post holes were 7 feet (2.1 m) in length and 2 feet (0.61 m) in width and formed sloping ramps to accommodate the insertion and raising of the estimated 20 feet (6.1 m) tall posts to a 4 feet (1.2 m) depth into the ground. When the holes were plotted out it was realized that they formed several arcs of equally spaced holes. Detailed analytical work supported the hypothesis that the placement of these posts was by design. Wittry hypothesized that the arcs could be whole circles and that the site was possibly a calendar for tracking solar events such as solstice and equinoxes. He began referring to the circles as "woodhenges"; comparing the structures to England's well-known circles at Woodhenge and Stonehenge.
Additional excavations were undertaken at the site by Dr. Robert L. Hall in 1963. Hall used the predicted locations from the arcs found in the previous excavation and was able to find more post holes as well as posts near the centers of the circles now thought to be central observation points. Wittry undertook another series of excavations at the site in the late 1970s and confirmed the existence of five separate timber circles in the general vicinity. The circles are now designated Woodhenges I through V in Roman numerals. Each was a different diameter and had a different number of posts. Because four of the circles overlap each other it is thought they were built in a sequence, with each iteration generally being larger and containing twelve more posts than its predecessor.
The remains of several posts were discovered in the post pits. The type of wood used, red cedar (Juniperus virginiana), is considered sacred by many Native American groups. The red cedar is the only native evergreen species in the area and is resistant to disease and decay. Traces of red ochre pigment was also found, suggesting that the posts were probably painted at some point. In 1985 William R. Iseminger led a series of excavations to finish finding a full circular sequence of posts. He was able to complete the sequence for what has become known as Woodhenge III (except for nine posts on the western edge that had been lost to dump trucks for road construction fill) and then led a reconstruction of the circle. The reconstruction team was able to obtain enough red cedar logs for half of the holes and then made do with black locust (Robinia pseudoacacia) for the other half; placing them into the original excavated post positions. The Illinois Historic Preservation Division (a division of the Illinois Department of Natural Resources) oversees the Cahokia site and hosts public sunrise observations at the vernal and autumnal equinoxes and the winter and summer solstices. Out of respect for Native American beliefs these events do not feature ceremonies or rituals of any kind.
The structure was rebuilt a number of times during the urban center's roughly 300 year history. The presence of single set posthole houses and midden deposits at the location suggests the area was a habitation area during the early Emergent Mississippian period; before the timber circles were constructed. And a separate layer of later Mississippian wall trench houses suggests it became a habitation area again after the final woodhenge was no longer in use.
- Woodhenge I was located to the east of the other circles, the only one not built on the same spot as the other four. It had 24 posts and was 240 feet (73 m) in diameter. This circle was dismantled and at a later date Mound 44 was constructed, partially covering this location.
- Woodhenge II was constructed to the west of the previous circle. It had 36 posts and was 408 feet (124 m) in diameter.
- Woodhenge III had 48 posts and was 410 feet (120 m) in diameter. It is thought to have been constructed in approximately 1000 CE. This version of the woodhenge was reconstructed in 1985 using the original holes found during excavations. The 48 posts of the circle are set at 7° 30′ (7 degrees 30 minutes) apart as measured from the geometric center of the circle, although the central post of the circle is offset from the true center by 5.6 feet (1.7 m) to the east. This facilitates the alignment with perimeter posts marking the winter and summer solstice sunrise positions, correcting for the latitude of Cahokias location.
- Woodhenge IV had 60 posts and was 476 feet (145 m) in diameter.
- Woodhenge V had an arc and post spacing that suggests it was 446 feet (136 m) in diameter and could have had 72 posts, although only 13 posts were found in a short arc facing the direction of the sunrise. Archaeologists suspect it may not have been a full timber circle and that by this time the large trees needed for the posts may have been getting scarce in the vicinity of Cahokia.
The woodhenge is thought by archaeologists to be a solar calendar, capable of marking equinox and solstice sunrises and sunsets for the timing of the agricultural cycle and religious observances. During the equinoxes the sun rises due east of the timber circle. From the vantage point of the center of the circle it appears as if the sun is emerging from the front of Monks Mound which is roughly .5 miles (0.80 km) away. One of the reasons for the changing position and size of the timber circles may have been the growing size of Monks Mound as additional layers of earth raised its height and increased its geographic footprint and the desire to keep this symbolic emergence and alignment intact.
The winter solstice sunrise pole is aligned with the Fox Mound (Mound 60, a rectangular platform mound paired with a conical burial mound, Mound 59) which sits across the grand plaza 1,640 feet (500 m) to the south of Monks Mound. The top of the roughly 46 feet (14 m) tall mound projects above the horizon and in Cahokian times would have had a large temple structure at its summit, raising it even higher. From the central pole of Woodhenge III the sun would have appeared to rise from this mound and temple at the winter solstice. Besides their celestial marking functions, the woodhenges also carried religious and ritual meaning that are reflected in their stylized depiction as a cross in circle motif on ceremonial beakers. One prominent example has markers added to the winter sunrise and sunset positions, and was found in an offertory pit near the winter solstice post pit. It also had radiating lines that probably symbolized the rays of the sun.
As there are many more posts than are necessary for these simple alignments some archaeoastronomists have speculated that they were also used to observe other celestial events, such as lunar cycles, the motion of the Pleiades, or other stars and planets; while others have suggested they were used to align mound and causeway constructions projects.
Other timber circles
Timber circles have a long history among Native American societies; their use stretches back for thousands of years and continues into the present day. From the 3400 year old Archaic period Poverty Point site in Louisiana to 2000 year old Hopewell tradition circles found in Ohio to the Sun Dance performed in wooden pole "corrals" by the Dhegihan-Siouan and Caddoan speaking peoples of the Great Plains. Archaeologist Timothy Pauketat has hypothesized that some Plains Indian medicine wheels and Sun Dance ceremonies may even be descendants of the Cahokia timber circles and their associated rituals and performances.
An early example of a timber circle witnessed by Europeans was recorded by watercolor artist John White in July 1585 when he visited the Algonquian village of Secotan in North Carolina. White was the artist-illustrator and mapmaker for the Roanoke Colony expedition sent by Walter Raleigh to begin the first attempts at British colonization of the Americas. White's works represent the sole-surviving visual record of the native inhabitants of the Americas as encountered by England's first colonizers on the Atlantic seaboard. Whites watercolor and the writings of the chronicler who accompanied him, Thomas Harriot, describes a great religious festival, possibly the Green Corn Ceremony, with participants holding a ceremonial dance at a timber circle. The posts of the circle were carved with faces. Harriot noted that many of the participants had come from surrounding villages and that "every man attyred in the most strange fashion they can devise havinge certayne marks on the backs to declare of what place they bee" and that "Three of the fayrest Virgins" danced around a central post at the center of the timber circle.
The oldest known timber circles in North American archaeology were found at Poverty Point in 2009 by archaeologists from the University of Louisiana at Monroe and Mississippi State University, led by Poverty Point station archaeologist Dr. Diana Greenlee. They discovered evidence in the 37.5 acres (15.2 ha) plaza area for multiple wooden post circular structures ranging from 82 feet (25 m) to 206 feet (63 m) in diameter; built during the earliest habitation of the site circa 2400 BCE. The site now has a ring of concrete posts marking the position of one of the circles.
Hopewell timber circles
Two examples have been found at Hopewell culture sites in Ohio. Moorehead Circle was constructed about two millennia ago at the Fort Ancient Earthworks near Lebanon, Ohio. It was discovered in 2005 by Jarrod Burks during magnetic surveys at the large hilltop earthen enclosure. The site consists of three concentric circles; with the outer circle being about 60 metres (200 ft) in diameter. Robert Riordan, Professor of Archaeology at Wright State University and lead archaeologist investigating the site, estimates that about two hundred wooden 10 feet (3.0 m) to 15 feet (4.6 m) tall posts were set in the outer circle. According to radiocarbon dates performed on charcoal found at the site, it was built between 40 BCE and 130 CE, with other charcoal fragments from burnt posts dating to 250 to 420 CE, suggesting the circle was in use for several centuries.
In September 2005 archaeologist Frank Cowan conducted excavations at the smaller circular enclosure at the Stubbs Earthworks in Warren County, Ohio; discovering a timber circle 240 feet (73 m) in diameter and composed of 172 large posts. Carbon dating of charcoal found in post molds at the site have dated the structure to 200-300 CE.
Mound 72 Woodhenge
Archaeologist Marvin Fowler has speculated that the woodhenges also served as “aligners” and that there may have been as many as three more in other strategic locations around the city of Cahokia, built to triangulate and lay out construction projects. At least one other possible circle at Cahokia has been put forward by Fowler, but his suggestion has not yet gained full acceptance by other archaeologists. This location was discovered near Mounds 72 and 96, directly to the south of Monks Mound. Several post holes of what may have been a ceremonial area with a 412 feet (126 m) in diameter circle and 48 posts. Archaeologists have dated the placement of at least one of the posts to approximately 950 CE. Archaeological research has shown that four of the posts were at the cardinal locations of north, south, east and west, with eastern and western posts marking the position of the equinox sunrise and sunsets. Four other posts in the circle were shown to be at the summer solstice sunrise and sunset and the winter solstice sunrise and sunset positions. This setup is nearly identical to the diameter and post positions of Woodhenge III, differing only in that Woodhenge III was 2 feet (0.61 m) smaller in diameter. The placement of the two mounds at the location and the directions in which they are oriented correspond to several of the solstice marking posts. The post nearest the later elite burial of the "Birdman" is the location that marked the summer solstice sunrise at the times of the sites use. The early stages of the mounds were actually constructed around the posts, although at a later point the posts were removed.
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