Ancient Sumer was located in modern-day southern Iraq. The Ancient Sumerians were known for many innovative achievements but the one that had the biggest impact, in my opinion, is their writing form cuneiform. It is the oldest known writing system in the world. I believe that this had the power to influence their development other achievements such as mathematics, art, economics, agriculture, government, and infrastructure.
Having a writing system assisted in communication and record keeping that allowed for those other areas to flourish and accommodate a successful society. Their successful record keeping and developments have assisted modern day society giving us a record of daily Sumerian life, large population accommodation, trade, art & literature, and government & leadership.