In ancient times, Iraq was known as Mesopotamia. The word Mesopotamia is Greek for "the land between the rivers," i.e. the Tigris and Euphrates rivers in western Asia. Despite this name, the ancient region of Mesopotamia included most of what is now Iraq, not just the land between the rivers. It also included parts of modern Syria and Turkey.

One of the world's earliest known civilizations, Sumer, arose in southern Mesopotamia around 3500 BC. Some scholars believe the Garden of Eden was in Iraq; the location seems to fit the Biblical description, and there are similarities between the Book of Genesis and Sumerian mythology.

The Sumerians have been credited with inventing, among other things, the calendar, the plow, the wheel, and writing. The early Sumerian city-states may even have practiced some form of democracy, but over time they became monarchies.

There were a number of city-states in Sumer, including Adab, Akshak, Badtibira, Eridu, Kish, Lagash, Larak, Larsa, Nippur, Sippar, Umma, Ur, and Uruk. A city-state consisted of the main city (sometimes more than one city), other towns and settlements, and surrounding lands. Each city-state was an independent kingdom, but sometimes one would dominate others.

The Sumerian King List, compiled in ancient times, provides some information about Sumer's royal dynasties. There are over a dozen different versions of the list, and many of the kings are said to have lived impossibly long lives, reigning for thousands of years. Still, there is evidence that some of the kings on the list really did exist.

One legendary king who seems to have been real was King Gilgamesh of Uruk. The Epic of Gilgamesh -- one of the world's oldest known written stories -- is a mythological account of Gilgamesh's search for immortality. The real King Gilgamesh lived around 2700 BC and was worshipped as a god after his death.

Perhaps the first king to truly unite Sumer was Lugalzagesi of Umma. He is said to have conquered all the other Sumerian city-states and then subjugated the rest of Mesopotamia and Syria. According to the inscription on an ancient vase, every other ruler bowed to Lugalzagesi, and he had no opponent "from where the sun rises to where the sun sets." But after 24 years on the throne (approximately 2340 to 2316 BC), he was overthrown by the great King Sargon of Akkad.

The Akkadian Empire

Akkad was a region in central Iraq, north of Sumeria. Although Akkadians and Sumerians spoke different languages, they had similar cultures.

Exactly how Sargon rose to power is not known. The location of his capital city, Agade, is unknown today. Even his real name is unknown; Sargon or Sharru-Kin is actually a title he gave himself meaning "the rightful king."

According to tradition, Sargon was born a commoner. He worked as a gardener, then as cupbearer to the king of Kish before somehow claiming the king's throne for himself. He went on to defeat Lugalzagesi and marched through Sumer, conquering cities and tearing down their walls. He fought 34 battles and reigned for 56 years. His empire included all of Akkad and Sumer, and parts of Asia Minor, Iran, and Syria. According to legend, he travelled as far as the Greek island of Crete. Even in old age, when a huge rebel force beseiged him at Agade, the mighty King Sargon led his army to victory.

Sargon's son and successor, Rimush, reigned for only nine years before being assassinated by members of his own court, possibly at the instigation of his brother Manishtusu, who replaced him as monarch. After 15 years on the throne, Manishtusu too was murdered. He was succeeded by his son Naram-Sin, who humbly called himself "King of the Universe." Naram-Sin's reign lasted from 2254 to 2218 BC. Like his grandfather Sargon, he was a great military leader who extended the Akkadian empire through conquest.

During the reign of Naram-Sin's son Shar-kali-sharri, Sumer and Akkad were invaded by a tribe of mountain people called the Guti or Gutians. Shar-kali-sharri managed to hang onto power for nearly a quarter century, but like Sargon's two sons he died in a palace coup. In the chaos that followed, the Akkadian empire fell apart.

Ur, Isin, and Larsa

The extent of the Guti's power in southern Mesopotamia over the next century is not certain, but they caused plenty of trouble before being defeated by a king from Uruk. Akkad and Sumer were then reunited under the third royal dynasty of Ur, which reigned over them for 108 years.

The third Ur dynasty's last king, Ibbi-Sin, inherited the throne around 2028 BC. During his reign, a nomadic people called the Amorites invaded Mesopotamia and established their own cities. To make matters worse for the king, one of his trusted officials, Ishbi-Erra, began usurping Ibbi-Sin's authority. Believing himself cursed by the god Enlil, Ibbi-Sin was unable to effectively resist Isbhi-Erra, who gradually took control of much of southern Mesopotamia.

The final blow came in 2004 BC, when invaders from Iran, the Elamites, destroyed Ur and took Ibbi-Sin captive. That was the end of the third royal dynasty of Ur.

Ishbi-Erra drove the Elamites out of Sumer and founded his own royal dynasty. His capital city was Isin. Although he and his successors called themselves kings of Ur and claimed dominion over all of Sumer and Akkad, there were many other kingdoms in Mesopotamia at that time. Eventually the kingdom of Larsa began taking over Isin's territory. Now it was the king of Larsa who claimed to be both "king of Ur" and "king of Sumer and Akkad." The last king of Isin, Damiq-ilishu, was deposed by King Rim-Sin of Larsa in 1794 BC.

Thirty years later, Rim-Sin was himself deposed by one of the greatest figures in Mesopotamian history: King Hammurabi of Babylon, founder of the Babylonian Empire.