Organized societies, in the ancient United States or Canada, were often mound builder civilizations. One of the most significant of these was the Poverty Point Culture that existed in the U.S state of Louisiana, and was responsible for the creation of over 100 mound sites. The Mississippi River was a core area in the development of long-distance trade and culture. Following Poverty Point, successive complex cultures such as the Hopewell emerged in the Southeastern United States in the Early Woodland period. Before 500 AD many mound builder societies, retained a hunter gatherer form of subsistence.