All of these all these prehistoric ceremonial earthworks in Ohio were created by what is now called the Hopewell Culture, a network of Native American societies that gathered from as far away as Montana and the Gulf of Mexico between roughly 100 BCE and 500 CE and were connected by a series of trade routes. Their earthworks in Ohio consist of shapes – like circles, squares and octagons – that were often connected to each other. Archaeologists are only now beginning to understand the sophistication of these engineering marvels.