Ancient American civilizations include notable cultures such as the Maya, Aztec, and Inca. These societies developed complex social structures, advanced agricultural techniques, and impressive architectural achievements. The Maya are known for their sophisticated writing system and calendar, while the Aztec built grand cities like Tenochtitlan and practiced intricate religious rituals. The Inca created an extensive road system across the Andes Mountains. These civilizations thrived in various regions, from Mesoamerica to the Andes. They engaged in trade, developed unique art forms, and made significant contributions to mathematics and astronomy. Despite their achievements, many faced challenges, including warfare and environmental changes, leading to their eventual decline.