The Sumerian civilization flourished from 4500 to 1750 BC in the southernmost region of Mesopotamia between the Euphrates and Tigris rivers (located in present-day southern Iraq). It was the earliest society to establish urban centers and city-states—among them, Eridu, Kish, Lagash, Nippur, Ur, and Uruk—and these became seats of exceptional inventiveness and cultural creativity. The most important innovations of the Sumerians included the first writing system (cuneiform), the first wheeled vehicles (and possibly the wheel itself), the potter’s wheel, the sailboat, the first legal codes of law (such as the Code of Ur-Nammu, from 2050 BC), and the first system for time measurement that divided a 24-hour day into 60-second minutes and 60-minute hours. The Sumerians were also responsible for tremendous agricultural advances, including the invention of the plow and the development of irrigation systems, intensive cultivation, and large-scale farming. See also: Agricultural science (animal); Agricultural science (plant); Agricultural soil and crop practices; Agriculture; Anthropology; Archeology; Domestication (anthropology); Irrigation (agriculture); Linguistics; Numbering systems; Phonetics; Time

The Sumerian system of writing, known as cuneiform, was an advance that completely revolutionized communication, enumeration (counting), bookkeeping, and literature. Cuneiform script utilized hundreds of wedge-shaped characters inscribed into wet clay tablets with a reed stylus. These tablets were then baked and hardened to preserve the information written on them. One of the earliest known works of literature is the Epic of Gilgamesh, which described the heroics of a Sumerian king and inspired many of the epic poems and stories of later cultures. In addition, cuneiform had a huge effect on commerce because it enabled Sumerian merchants and traders to accurately record and keep track of an enormous volume of business matters, leading to increased trade with foreign lands. See also: Clay; Literature of science and technology

By approximately 1750 BC, the Sumerians had been, in effect, conquered and assimilated into the Akkadian and Babylonian kingdoms that arose in the northern areas of Mesopotamia. However, many of the Sumerian innovations, especially their most important advances in cuneiform writing, city-state planning, record keeping, and agriculture, were incorporated into these later civilizations.