Scotland has Stonehenge, Cahokia has Woodhenge. Woodhenge was, historically, an observatory for watching the sun, moon, and star cycles, built on land once used for houses in the early Emergent Mississippian era. There were five observatories at Cahokia. Wood posts, made of sacred red cedar reached toward the sky. The resulting shadows provided scientific data the people needed for their studies and to properly time religious ceremonies and agricultural cycles. The five observatories were probably built at different times because each Woodhenge had a larger diameter and twelve more posts than the one it overlapped. Woodhenge 1 had twenty-four posts. The last Woodhenge, Woodhenge 5 had 72 posts. Archaeologists believe Woodhenge 1 was built in 900 CE, was in use for much of Cahokia’s history, then just stopped being used around 1100 CE. Woodhenge likely returned to its original residential use, based on archaeology at the site.