without rainfall to nourish crops, without trees or stones for building.

In spite of all this, its inhabitants built the world's first cities,

with monumental architecture and large populations—

and they built them entirely out of mud.

Sumer occupied the southern part of modern Iraq

in the region called Mesopotamia.

Mesopotamia means “between two rivers”—

the Tigris and the Euphrates.

Around 5000 BCE, early Sumerians used irrigation channels, dams, and reservoirs

to redirect river water and farm large areas of previously bone-dry land.

Agricultural communities like this were slowly springing up around the world.

But Sumerians were the first to take the next step.

Using clay bricks made from river mud,

they began to build multi-storied homes and temples.

They invented the wheel—

a potter's wheel, for turning mud into household goods and tools.

Those clay bricks gave rise to the world's first cities,

probably around 4500 BCE.

At the top of the city's social ladder were priests and priestesses,

who were considered nobility,

then merchants, craftspeople, farmers, and enslaved people.

The Sumerian empire consisted of distinct city-states

that operated like small nations.

They were loosely linked by language and spiritual belief

but lacked centralized control.

The earliest cities were Uruk, Ur, and Eridu,

and eventually there were a dozen cities.

Each had a king who served a role somewhere between a priest and a ruler.

Sometimes they fought against each other to conquer new territories.

Each city was dedicated to a patron deity, considered the city's founder.

The largest and most important building in the city was this patron god's home:

the ziggurat, a temple designed as a stepped pyramid.

Around 3200 BCE, Sumerians began to expand their reach.

The potter's wheel found a new home on chariots and wagons.

They built boats out of reeds and date palm leaves,

with linen sails that carried them vast distances by river and sea.

To supplement scarce resources, they built a trade network

with the rising kingdoms in Egypt, Anatolia, and Ethiopia,

importing gold, silver, lapis lazuli, and cedar wood.

Trade was the unlikely impetus

for the invention of the world's first writing system.

It started as a system of accounting for Sumerian merchants

conducting business with traders abroad.

After a few hundred years, the early pictogram system

called cuneiform turned into a script.

The Sumerians drafted up the first written laws

and created the first school system, designed to teach the craft of writing—

and pioneered some less exciting innovations, like bureaucracy and taxes.

In the schools, scribes studying from dawn to dusk,

from childhood well into adulthood.

They learned accounting, mathematics, and copied works of literature—

hymns, myths, proverbs, animal fables, magic spells,

and the first epics on clay tablets.

Some of those tablets told the story of Gilgamesh,

a king of the city of Uruk who was also the subject of mythical tales.

But by the third millennium BCE, Sumer was no longer the only empire around,

or even in Mesopotamia.

Waves of nomadic tribes poured into the region from the north and east.

Some newcomers looked up to the Sumerians, adopting their way of life

and using the cuneiform script to express their own languages.

In 2300 BCE, the Akkadian king Sargon conquered the Sumerian city-states.

But Sargon respected Sumerian culture,

and Akkadians and Sumerians existed side-by-side for centuries.

Other invading groups focused only on looting and destruction.

Even as Sumerian culture spread,

a steady onslaught of invasions killed off the Sumerian people by 1750 BCE.

Afterward, Sumer disappeared back into the desert dirt,

not to be rediscovered until the 19th century.

But Sumerian culture lived on for thousands of years—

first through the Akkadians, then the Assyrians, then the Babylonians.

The Babylonians passed Sumerian inventions and traditions through

along Hebrew, Greek, and Roman cultures.

Some persist today.