Native American Indians of the Mississippian culture were sun worshipers and had a highly complex warfare culture. Their symbols, such as the Thunderbird symbol, reflect the warfare culture and the religious beliefs and cosmologies of the different historic tribes who existed at the time of the first European contact.
The Mississippians believed that the universe consisted of three parts with good and bad spiritual forces. These three worlds were linked together and their connection was usually portrayed as a cedar tree or a striped pole. The Underworld was inhabited by spirit snakes, the Upper world was inhabited by spirit birds and the people of the earth who were ruled by these powerful spirits like the Thunderbird.
Items displaying symbols, like the Thunderbird symbol, from the Mississippian culture have been found in burial sites that contained war axes, knives and other weapons. This type of symbol was embossed in valuable materials such as rare shells, copper and lead and depicted on pottery and stone tools and weapons.