<P> Some effigy mounds were constructed in the shapes or outlines of culturally significant animals . The most famous effigy mound, Serpent Mound in southern Ohio, ranges from 1 to just over 3 ft tall (30--100 cm)., 20 ft (6 m) wide, more than 1,330 ft (405 m) long, and shaped as an undulating serpent . </P> <P> Many different tribal groups and chiefdoms, involving an array of beliefs and unique cultures over thousands of years, built mounds as expressions of their cultures . The general term, "mound builder", covered their shared architectural practice of earthwork mound construction . This practice, believed to be associated with a cosmology that had a cross-cultural appeal, may indicate common cultural antecedents . The first mound building was an early marker of political and social complexity among the cultures in the Eastern United States . Watson Brake in Louisiana, constructed about 3500 BCE during the Middle Archaic period, is the oldest dated mound complex in North America . It is one of 11 mound complexes from this period found in the Lower Mississippi Valley . </P> <P> These mound builders were organized; hundreds or even thousands of workers had to dig up tons of earth with the hand tools available, the soil had to be moved long distances, and finally, workers had to create the shape the builder had planned . </P> <P> The most complete reference for these earthworks is Ancient Monuments of the Mississippi Valley, written by Ephraim G. Squier and Edwin H. Davis . It was published in 1848 by the Smithsonian Institution . Since many of the features which the authors documented have since been destroyed or diminished by farming and development, their surveys, sketches, and descriptions are still used by modern archaeologists . All of the sites which they identified as located in Kentucky came from the manuscripts of C.S. Rafinesque . </P>

Who created earth mounds in what is now the state of ohio ​