Over 9,000 years ago in Mexico, ancient people domesticated corn and developed basic calendars for farming, leading to the first civilizations in North America. Many advanced civilizations developed across North America, including the Olmec, Zapotec, Maya, Toltec, Mexica (Aztec), Mississippian, Anasazi and others. These civilizations built large cities and structures like pyramids, and made contributions in astronomy, mathematics, medicine, engineering and more before Europeans arrived.