The Sumerian culture region is the earliest known civilization in the region, and it was located in southern Mesopotamia. The Akkadian Empire followed the Sumerians, and it was centered in northern Mesopotamia. The Assyrian Empire was the last of the great Mesopotamian empires, and it was also centered in northern Mesopotamia.
The similarities in the locations of these civilizations can be attributed to the fact that the region is very well-suited for human habitation. The fertile land, the rivers, and the mild climate all made it an ideal place for early civilizations to develop.