<Table> <Tr> <Td> </Td> <Td> This article needs additional citations for verification . Please help improve this article by adding citations to reliable sources . Unsourced material may be challenged and removed . (January 2011) (Learn how and when to remove this template message) </Td> </Tr> </Table> <Tr> <Td> </Td> <Td> This article needs additional citations for verification . Please help improve this article by adding citations to reliable sources . Unsourced material may be challenged and removed . (January 2011) (Learn how and when to remove this template message) </Td> </Tr> <P> An effigy mound is a raised pile of earth built in the shape of a stylized animal, symbol, human, or other figure and generally containing one or more human burials . Effigy mounds were primarily built during the Late Woodland Period (350 - 1300 CE (current era)). Conical and linear mounds, the predecessors of effigy mounds may date from as far back as 700 BCE (before the current era). They remain places First Peoples frequent to visit and speak with ancestors, to put down tobacco and to give thanks . These sites are primarily visited by Hochungra (pl. of Hochunk) people whose ancestors likely built the great majority of them, though they are also visited by people from other original indigenous nations such as Anishinaabe (Ojibwe), Kikapu, Oneida, Menominii who reside in Wisconsin and surrounding areas . There also remains the possibility that a greater diversity of First Peoples such as ancestors of those named nations may have contributed to building some percentage of the mounds . That is to say that ancestral Hochunk likely popularized the form and other groups may have adopted the practice of building effigy mounds from having observed the Hochunk ancestors methods and aesthetics surrounding their construction . </P> <P> Scholars believe that effigy mounds were built primarily for spiritual purposes, although most also fulfilled a burial mound function . According to 2011 ground - penetrating radar and magnetometry studies surveying 586 mounds at 128 sites, 65% of linear mounds in Wisconsin contain evidence of burials, 89% of conical mounds contain evidence of burials, and 87% of effigy (animal and other abstract shaped) mounds contain persistent evidence of burials . Older conical mound construction evolves into effigy mound construction over time . Given the expected rates of decay regarding burial evidence (some conical mounds being as old as 2700 years) it is reasonable to project that all mounds in the conical - to - effigy mound spectrum, are burial or funerary earthworks . The builders of the effigy mounds are usually referred to as the Mound Builders . Native American societies in Wisconsin built more effigy mounds than did those in any other region of North America--between 15,000 and 20,000 mounds, at least 4,000 of which remain today . Many mounds on the University of Wisconsin grounds including burial mounds measuring as large as 35 feet in diameter and 5 feet high were removed for grading (ground leveling) purposes as recently as 1909 . </P>

When were most of the effigy mounds built