Ancient Sumer was comprised of a network of discrete city-states. While they shared the Sumerian language in common, each city-state was its own polity or political entity.
Sumerians were among the earliest settlers in ancient Mesopotamia. By 4,000 B.C. the people had organized themselves into separate city-states, which were in a state of constant warfare. They battled each other about key economic, political and social resources. Each city-state was governed by a king and had several holy temples, or ziggurats, dedicated to the different gods and goddesses they worshipped.
The social class system was as follows, in order of highest to lowest: kings and priests, merchants, scribes and artisans, and lastly, farmers.