Effigy Mounds National Monument

Effigy Mounds National Monument, in northeastern Iowa, was established in 1949 to preserve 191 prehistoric burial mounds within a 1,481-acre area of the Mississippi River Valley. Unlike other earthen burial mounds built by the prehistoric Indians of North America, these are in the shape of bears, birds, and geometric figures. The largest, Great Bear Mound, is 137 feet long. Built over hundreds of years, from 500 to about 1500 AD, the mounds are the work of three different Indian groups of the Middle and Late Eastern Woodlands tradition, distinguished by archaeologists on the basis of the different styles of tools, weapons, and other artifacts.