The term "Mound Builders" refers to various ancient Native American cultures that constructed earthen mounds for various purposes, including burial, ceremonial, and residential uses. These cultures thrived in regions of North America, particularly in the Ohio River Valley, Mississippi River Valley, and the Great Lakes area. The mounds vary in size and shape, with some resembling animals or geometric forms. The most well-known Mound Builders include the Hopewell and Mississippian cultures. The Hopewell culture, which flourished from around 200 BCE to 500 CE, is noted for its elaborate burial mounds and trade networks. The Mississippian culture, emerging around 800 CE, is recognized for its large, complex societies and monumental mounds, such as those found at Cahokia.