Effigy Mounds National Monument preserves more than 200 prehistoric mounds built by pre-Columbian Mound Builder cultures, mostly in the first millennium CE, during the later part of the Woodland period of pre-Columbian North America. Numerous effigy mounds are shaped like animals, including bears and birds.

An effigy mound is a raised pile of earth built in the shape of a stylized animal, symbol, religious figure, human, or other figure. The Effigy Moundbuilder culture is primarily associated with the years 550–1200 CE during the Late Woodland Period, although radiocarbon dating has placed the origin of certain mounds as far back as 320 BCE.