The Mississippi Valley was very attractive for early colonizers. The Spaniards first went there in 1541, hoping they would find gold just like their fellow citizens had done in Mexico two decades earlier. But their venture didn't bear any fruit. Then, in 1673, French came to explore the land. Soon enough, missionaries followed their steps, and the first small settlements were formed, in spite of many troubles (such as outbreaks of smallpox).
One of the most important was climate changes. As climate changed, nomads had to find new places to migrate to which led to people going to areas that were uninhabited before. Another was the development of agriculture which more or less ended the nomadic way of life when people started settling.
Noah in the biblical sense like Noah’s ark