Sumerian civilization

Sumer was the first urban civilization in the historical region of southern Mesopotamia, modern-day southern Iraq, during the Chalcolithic and Early Bronze ages, and arguably the first civilization in the world with Ancient Egypt and the Indus Valley.

Living along the valleys of the Tigris and Euphrates, Sumerian farmers were able to grow an abundance of grain and other crops, the surplus of which enabled them to settle in one place - wikipedia