Gilgamesh, the Story
Gilgamesh, the story of the great Sumerian king of the same name, is considered the oldest surviving epic on Earth.  The real-life King Gilgamesh is believed to have reigned in Sumeria around 2700 to 2500 BC.  Legends state that Gilgamesh ruled for 126 "years," although a "year" may have been measured by seasons or moon phases.  Gilgamesh is 2/3 god and 1/3 man, being the son of the goddess Ninsun and Priest Kullab.
There are many authors of Gilgamesh, a story written on 12 clay tablets, found in the library of the Assyrian king Assurbanipal.  Ancients described this story as The Gilgamesh Cycle, a poem of 12 songs (cantos), 300 lines each.  Today, the tablets are worn and chipped, so parts of dozens of lines have been lost forever.  Still, the wisdom of this story remains for us to enjoy today.  Gilgamesh begins: Sha nagba imuru ("he who saw everything").  Originally, the epic would have been recited and accompanied by musical instruments such as lyres, harps, reed pipes, and drums.
 

The Fertile Crescent
Civilizations, as we know them, began in the flat, fertile land between the Tigris and Euphrates River valley (presently, modern Iraq).  Although this area has been home to hundreds of different cultures over the ages, the sudden development of educated, governed cultures in this area around 3000-2800 BC became known as Mesopotamia.  The Mesopotamians divided their history into two parts: before and after the Great Flood.  Before the flood, the priests and sages ruled the land, receiving their instruction from their god Ea, the god of waters and wisdom.  After the flood, kings like Gilgamesh ruled the land.

The Sumerians became the first literate culture in Mesopotamia, and the first to develop schools.  They developed a number system based on 60.  Today, our 60-second minute and our 60-minute hour originate with the ancient Sumerians (as does our 360 degree circle).  The Sumerians were also the first culture to create great cities that acted like independent nations, even though they were within each other's view.  These cities were built around tall ziggurats, six- or seven-story stepped temples that served as staircases used by the gods when they descended from the heavens.  One of the greatest Sumerian cities was Uruk, founded by Gilgamesh's semi-divine father, Lugulbanda, who was supposed to have reigned for thousands of years.  Gilgamesh became an even greater leader by acquiring lumber and building a great protective wall around the city.

Between 2500 and 500 BC, Mesopotamia was filled with ongoing wars between the ever-populating cultures.  In 2300 BC, the Babylonians defeated the Sumerians and adopted their culture.  The Babylonians were the first culture to record the Sumerian epic in its present form: they added the flood story and the prologue (a thousand years before the Hebrew Old Testament was composed).
 

Glossary
Babylon = "the gate of the gods"
cuneiform = "wedge"
Humbaba = 'the battering ram"
Mesopotamia = "the land between the rivers"

archetype = a pattern or theme that recurs in many different cultures
epic = the protagonist is a human
myth = the protagonist is a god