A prehistoric solar calendar

At least five large post-circle monuments were built at this location from AD 1100 to 1200, each with a different diameter and number of posts. Woodhenge III is the circle most extensively excavated and is the one reconstructed here, in the original location.

The sun rising above the bluffs to the east aligns with certain posts on the perimeter, as viewed from the central observation post. The most important alignments are the winter and summer solstices, marking the southernmost and northernmost sunrise positions, and the fall and spring equinoxes, when the sun rises due east, midway between the solstice posts. Also, at the equinoxes the rising sun appears to emerge from the front of Monks Mound, perhaps confirming a link between the sun and the chief who ruled from the top of the mound.

The excavations also revealed hundreds of houses and pits, showing this was a residential area before and after the construction of the Woodhenges. Fragments of wood in some of the holes indicate that red cedar, a sacred wood for most Indians, was used for the posts.


(Center Left Illustration Caption)
Drawing of a reconstructed beaker from fragments found in a pit near the winter solstice pole. Its symbols represent the sun (radiating lines), earth and the four directions (circle and cross).

(Lower Center Image Caption)
Equinox and solstice sunrise observances are held on the Sunday morning closest to the event so that more people are able to attend and learn about this solar calendar monument.

(Lower Center Diagram Caption)
Woodhenge III was reconstructed on its original site. Observer's post is slightly east of center point to form an angle of 30.8 degrees needed to sight solstices at this latitude.

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Monks Mound
Grand Plaza
Cahokia
Stockade
N. 13th St. and Nectar Ave.
N. 9th St. and Gross Ave.
N. 18th St. and Parsons Ave.
N. 9th St. & St. Clair Ave.
1010 Pennsylvania Avenue
621 N. 9th Street

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