The earliest inhabitants of the Americas came from Asia. They eventually settled as far as the southern tip of South America. How the various groups lived was influenced by the geography and climate of their particular region. People who settled in the northeastern part of North America developed a high level of political organization. By the late 1500s, several groups in this area had formed the Iroquois League to maintain peace. The League's representative structure provided a flexible but stable system of government. Powerful empires emerged in the Americas, especially the Maya and Aztec in Mexico and Central America and the Inca in South America. They built large ceremonial centers that included temple-pyramids, marketplaces, and palaces. Religion, science, mathematics, and engineering were important in daily life.