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Bill Iseminger

Welcome spring at Cahokia Mounds

Witness dawn at ‘Woodhenge’ on March 23 to celebrate spring amid prehistoric mounds

COLLINSVILLE, Ill. – Cahokia Mounds State Historic Site welcomes spring with a special event Sunday at dawn at “Woodhenge,” a reconstruction of the calendar used to mark astronomical events when the mounds were home to thousands of Native Americans. 

Sun-watchers will see how the calendar shows the vernal equinox, when day and night are equal in length and spring officially begins. (It took place on Thursday this year, but Cahokia Mounds is holding its event on a day when more people are able to come and learn about Woodhenge.)

The huge circle of posts stands about half a mile west of the site’s Interpretive Center on Collinsville Road. The reconstruction – 48 posts in a 410-foot circle – represents one of five calendars built at the location between the years 1100 and 1200. From the central observation post, the rising sun aligns with posts marking dates in the ritual calendar of the Mississippian Indians.

The event begins at 6:45 a.m. No ceremonies will be held, out of respect for Native American beliefs, but an expert will explain how Woodhenge was discovered, how it works and what we know about it and the culture of this ancient city.

Cahokia Mounds State Historic Site, administered by the Illinois Historic Preservation Agency, is just eight miles from downtown St. Louis off Interstates 55/70 (Exit 6) and Interstate 255 (Exit 24). The Interpretive Center is open 9 a.m. - 5 p.​m. Wednesday through Sunday. 

For more information, call 618-346-5160 or go to