Sumer ( SOO-mər) is the earliest known civilization, located in the historical region of southern Mesopotamia (now south-central Iraq), emerging during the Chalcolithic and early Bronze Ages between the 5th and 4th millennium BC. Like nearby Elam, it is one of the cradles of civilization, along with Egypt, the Indus Valley, the Erligang culture of the Yellow River valley, Caral-Supe, and Mesoamerica. Living along the valleys of the Tigris and Euphrates rivers, Sumerian farmers grew an abundance of grain and other crops, a surplus of which enabled them to form urban settlements. The world's earliest known texts come from the Sumerian cities of Uruk and Jemdet Nasr, and date to between c. 3350 – c. 2500 BC, following a period of proto-writing c. 4000 – c. 2500 BC.
Name
The term "Sumer" (Akkadian: 𒋗𒈨𒊒, romanized: šumeru) comes from the Akkadian name for the "Sumerians", the ancient non-Semitic-speaking inhabitants of southern Mesopotamia. In their inscriptions, the Sumerians called their land "Kengir", the "Country of the noble lords" (Sumerian: 𒆠𒂗𒄀, romanized: ki-en-gi(-r), lit. ''country" + "lords" + "noble''), and their language "Emegir" (Sumerian: 𒅴𒂠, romanized: eme-g̃ir or 𒅴𒄀 eme-gi15).
The Akkadians, the East Semitic-speaking people who later conquered the Sumerian city-states, gave Sumer its main historical name, but the phonological development of the term šumerû is uncertain. Hebrew שִׁנְעָר Šinʿar, Egyptian Sngr, and Hittite Šanhar(a), all referring to southern Mesopotamia, could potentailly be western variants of Sumer.

Origins
Most historians have suggested that Sumer was first permanently settled between c. 5500 and c. 3300 BC by a West Asian people who spoke the Sumerian language (pointing to the names of cities, rivers, basic occupations, etc., as evidence), a non-Semitic and non-Indo-European agglutinative language isolate.
Others have suggested that the Sumerians were a North African people who migrated from the Green Sahara into the Middle East and were responsible for the spread of farming in the Middle East. However, contrary evidence strongly suggests that the first farming originated in the Fertile Crescent. Although not specifically discussing Sumerians, Lazaridis et al. 2016 have suggested a mix of basal Eurasian and western Eurasian hunter-gatherer ancestry for the pre-Semitic peoples of the fertile crescent, particularly the Natufians, after testing the genomes of Natufian and other Pre-Pottery Neolithic culture-bearers.
Some scholars associate the Sumerians with the Hurrians and Urartians, and suggest the Caucasus as their homeland. This is not generally accepted.

Based on mentions of Dilmun as the "home city of the land of Sumer" in Sumerian legends and literature, other scholars have suggested the possibility that the Sumerians originated from Dilmun, which was theorized to be the island of Bahrain in the Persian Gulf. In Sumerian mythology, Dilmun was also mentioned as the home of deities such as Enki. The status of Dilmun as the Sumerians’ ancestral homeland has not been established, but archaeologists have found evidence of civilization in Bahrain, namely the existence of Mesopotamian-style round disks.
A prehistoric people who lived in the region before the Sumerians have been termed the "Proto-Euphrateans" or "Ubaidians", and are theorized to have evolved from the Samarra culture of northern Mesopotamia. The Ubaidians, though never mentioned by the Sumerians themselves, are assumed by modern-day scholars to have been the first civilizing force in Sumer. They drained the marshes for agriculture, developed trade, and established industries, including weaving, leatherwork, metalwork, masonry, and pottery.
Some scholars contest the idea of a Proto-Euphratean language or one substrate language; they think the Sumerian language may originally have been that of the hunting and fishing peoples who lived in the marshland and the Eastern Arabia littoral region and were part of the Arabian bifacial culture. Juris Zarins believes the Sumerians lived along the coast of Eastern Arabia, today's Persian Gulf region, before it was flooded at the end of the Ice Age.

Sumerian civilization took form in the Uruk period (4th millennium BC), continuing into the Jemdet Nasr and Early Dynastic periods. The Sumerian city of Eridu, on the coast of the Persian Gulf, is considered to have been one of the oldest cities, where three separate cultures may have fused: that of peasant Ubaidian farmers, living in mud-brick huts and practicing irrigation; that of mobile nomadic Semitic pastoralists living in black tents and following herds of sheep and goats; and that of fisher folk, living in reed huts in the marshlands, who may have been the ancestors of the Sumerians.
Reliable historical records begin with Enmebaragesi (Early Dynastic I). The Sumerians progressively lost control to Semitic states from the northwest. Sumer was conquered by the Semitic-speaking kings of the Akkadian Empire around 2270 BC (short chronology), but Sumerian continued as a sacred language. Native Sumerian rule re-emerged for about a century in the Third Dynasty of Ur at approximately 2100–2000 BC, but the Akkadian language also remained in use for some time.
Archeological discovery
The Sumerians were entirely unknown during the early period of modern archeology. Jules Oppert was the first scholar to publish the word Sumer in a lecture on 17 January 1869. The first major excavations of Sumerian cities were in 1877 at Girsu by the French archeologist Ernest de Sarzec, in 1889 at Nippur by John Punnett Peters from the University of Pennsylvania between 1889 and 1900, and in Shuruppak by German archeologist Robert Koldewey in 1902–1903. Major publications of these finds were "Decouvertes en Chaldée par Ernest de Sarzec" by Léon Heuzey in 1884, "Les Inscriptions de Sumer et d'Akkad" by François Thureau-Dangin in 1905, and "Grundzüge der sumerischen Grammatik" on Sumerian grammar by Arno Poebel in 1923.

City-states in Mesopotamia
In the late 4th millennium BC, Sumer was divided into many independent city-states, which were divided by canals and boundary stones. Each was centered on a temple dedicated to the particular patron god or goddess of the city and ruled over by a priestly governor (ensi) or by a king (lugal) who was intimately tied to the city's religious rites.
An incomplete list of cities that may have been visited, interacted and traded with, invaded, conquered, destroyed, occupied, colonized by and/or otherwise within the Sumerians’ sphere of influence (ordered from south to north):
Eridu (Tell Abu Shahrain)SC

Kuara (probably Tell al-Lahm)SU
Ur (Tell al-Muqayyar)SC
Kesh (probably Tell Jidr)SU

Larsa (Tell as-Senkereh)S
Uruk (Warka)SC
Bad-tibira (probably Tell al-Madain)SC
Lagash (Tell al-Hiba)S
Girsu (Tello or Telloh)S
Umma (Tell Jokha)S
Zabala (Tell Ibzeikh)S
Shuruppak (Tell Fara)SC
Kisurra (Tell Abu Hatab)S
Mashkan-shapir (Tell Abu Duwari)S
Eresh (probably Abu Salabikh) SU
Isin (Ishan al-Bahriyat)SC
Adab (Tell Bismaya)SC
Nippur (Afak)SH
Marad (Tell Wannat es-Sadum)S
Dilbat (Tell ed-Duleim)S
Borsippa (Birs Nimrud)M
Larak (probably Tell al-Wilayah)SCU
Kish (Tell Uheimir and Ingharra)MC
Kutha (Tell Ibrahim)M
Sippar (Tell Abu Habbah)MC
Der (al-Badra)M
Akshak (probably Tell Rishad)MCU
Akkad (probably Tell Mizyad)MCU
Eshnunna (Tell Asmar)M
Awan (probably Godin Tepe)ICU
Mari (Tell Hariri)WC
Hamazi (probably Kani Jowez)NCU
Nagar (Tell Brak)W
Apart from Mari, which lies full 330 kilometres (205 miles) north-west of Agade, but which is credited in the king list as having exercised kingship in the Early Dynastic II period, and Nagar, an outpost, these cities are all in the Euphrates-Tigris alluvial plain, south of Baghdad in what are now the Bābil, Diyala, Wāsit, Dhi Qar, Basra, Al-Muthannā and Al-Qādisiyyah governorates of Iraq.
History
The Sumerian city-states rose to power during the prehistoric Ubaid and Uruk periods. Sumerian written history reaches back to the 27th century BC and before, but the historical record remains obscure until the Early Dynastic III period, c. 23rd century BC, when the language of the written records becomes easier to decipher, which has allowed archaeologists to read contemporary records and inscriptions.
The Akkadian Empire was the first state that successfully united larger parts of Mesopotamia in the 23rd century BC. After the Gutian period, the Ur III kingdom similarly united parts of northern and southern Mesopotamia. It ended in the face of Amorite incursions at the beginning of the second millennium BC. The Amorite "dynasty of Isin" persisted until c. 1700 BC, when Mesopotamia was united under Babylonian rule.
New Stone Age: c. 10000 – c. 5000 BC
Ubaid period: c. 6500 – c. 4100 BC
Copper Age: c. 5000 – c. 3300 BC
Uruk period: c. 4100 – c. 3100 BC
Uruk XIV–V phases: c. 4100 – c. 3300 BC