Sumer rose as Mesopotamia's first civilization around 3500 B.C.

Sumer was made up of 12 independent city-states

City-States were cities with its surrounding lands and settlements, governed by the city-state rulers

City-States developed from early villages after they united to form major irrigation projects for farming

These city-states also fished and traded

Often, city-states would engage in wars with each other for control of fertile lands, resources, and trade routes

City-States, like Sumer and Ur, were founded along the Tigris and Euphrates Rivers

Some city-states gathered and settled near the coast of the Persian Gulf

City-States near the coast fished and traded

Successful farming and fishing allowed the peoples of Mesopotamia to raise a surplus of food

A surplus of food gave these peoples more free time to specialize in new skills (making artisan crafts, etc.)

They began to trade for goods that they didn't have, like copper and tin, to make new products

They made bronze with tin and copper (The beginning of the Bronze Age) 

Mesopotamians began making strong bronze tools and weapons

The Bronze Age began around 3000 B.C.

With a food surplus, population grew quickly

With a large population, a form of government and social classes were put in place

Kings emerged to provide leadership

Government officials collected taxes and kept order

The social classes were: King at the top, Priests were next, Government Administrators, Scribes (writers), merchants (traders, store owners, etc.), and Artisans (skilled workers that made hand-made goods)

At the bottom of the class system were farmers and less-skilled workers (laborers)

Slaves were below even the farmers and low-skilled workers