The Mayan civilization flourished from around 300 BCE to 900 CE in Mesoamerica. During this time, they developed advanced achievements in mathematics, astronomy, and architecture. They invented the first known writing system in the Americas, calculated an accurate solar year of 365 days, and built large pyramid structures. While the Mayan empire declined around 900 CE, the exact causes are still debated but likely involved environmental degradation, overpopulation, and political instability.