The people who established the world's first civilization around 3500 B.C. in southern Mesopotamia were known as the Sumerians.

The Sumerians learned to control the Tigris and Euphrates Rivers by constructing levees and irrigation canals. As a result, a stable food supply existed, and the Sumerian villages evolved into self-governing city-states.

At the center of each city-state was a temple surrounded by courts and public buildings. Radiating from the all-important city center were the two-story houses of the priests and merchants, or the upper class; the one-story homes of government officials, shopkeepers, and craftspeople; and the lower class homes of farmers, unskilled workers, and fishermen. The city-state also included the fertile farming land outside the city wall.

Since there wasn't any building stone and very little timber in Sumer, the people constructed their homes, public buildings, and city walls out of sun-dried mud brick.

The Sumerians took great pride in their city-states. Many times city-states would war with each other because boundary disputes existed. Sometimes a city-state would attack a neighboring city-state just to prove its strength.