從考古發現已經得到的史料來看，從公元前2900年開始，蘇美爾城邦進入一個“諸國爭霸”的時代。
比較大的城市有埃利都、基什、拉格什、烏魯剋、烏爾和尼普爾。這些城市因水權、貿易道路和遊牧民族的進貢等事務進行了幾乎一千年的、為時不斷的互相爭戰。考古已經能大致勾勒出當時的歷史情況，但是由於考古發現的史料有限，今天人們所知道的那段歷史可能仍然是當時實際情況的冰山一角而已。
基什被認為曾經是一個比較強大的城邦，因為後來許多蘇美爾君主甚至並沒有實際統治過基什，卻也自稱基什之王。（不過現在也有歷史學家認為，這並不足以說明基什曾經稱霸，自稱基什之王可能有其他的比如宗教方面的原因）最早的可以驗證是存在的國王就是基什國王恩美巴拉格西。
後來一些比較強大的城邦是烏魯剋，烏爾，溫馬，以及拉格什等。
考古學家在拉格什發現了王室的銘文，使得今天的人們得以知道從公元前2500年到公元前2350年之間約一百五十年間的完整的拉格什國王列表，以及相關的史事，也使得拉格什成為蘇美爾各城邦中，今天的人們瞭解的唯一比較完整的城邦.
“約公元前2500年左右，拉格什強大起來，烏爾南什王時，拉格什在蘇美爾中稱霸，到了安那葉姆王和恩鐵美那王時，拉格什徵服了不少地方，蘇美爾頗有統一的趨勢。後來，國王盧加爾安達因治國不善，引起了暴動，一個名叫烏魯卡基那的人推翻了盧加爾安達的統治，在平民的擁護下，自己登上了王位，並進行了已知人類歷史上第一次政治改革運動，試圖維護平民的利益。正當拉格什內亂之時，蘇美爾各國爆發了大規模的戰爭，溫馬王盧加爾紮剋西徵服拉格什，殺死烏魯卡基那。血屠全城。烏魯卡基那在位僅六年，他的改革也因此而廢棄。”
溫馬的祭司國王盧加爾紮剋西（Lugal-Zage-Si，公元前2259～公元前2235年）消滅拉格什的王朝，占領烏魯剋，並將它作為他的首都，他自稱他的帝國從波斯灣一直蔓延到地中海。
但是閃族的阿卡德國王薩爾貢打敗了盧加爾紮剋西，俘虜了他，而蘇美爾人城邦的歷史也就就此結束了。
Early Dynastic period (Early Bronze Age II-IV)
* Early Dynastic I period: 2900 – 2800 BC
* Early Dynastic II period: 2800 – 2600 BC (Gilgamesh)
* Early Dynastic IIIa period: 2600 – 2500 BC
* Early Dynastic IIIb period: ca. 2500 – 2334 BC
The Dynastic period begins ca. 2900 BC and includes such legendary figures as Enmerkar and Gilgamesh—who are supposed to have reigned shortly before the historic record opens ca. 2700 BC, when the now decipherable syllabic writing started to develop from the early pictograms. The center of Sumerian culture remained in southern Mesopotamia, even though rulers soon began expanding into neighboring areas, and neighboring Semitic groups adopted much of Sumerian culture for their own.
The earliest Dynastic king on the Sumerian king list whose name is known from any other legendary source is Etana, 13th king of the first Dynasty of Kish. The earliest king authenticated through archaeological evidence is Enmebaragesi of Kish (ca. 26th century BC), whose name is also mentioned in the Gilgamesh epic—leading to the suggestion that Gilgamesh himself might have been a historical king of Uruk.
1st Dynasty of Lagash
ca. 2500 – 2270 BC
The dynasty of Lagash, though omitted from the king list, is well attested through several important monuments and many archaeological finds.
Although short-lived, one of the first empires known to history was that of Eannatum of Lagash, who annexed practically all of Sumer, including Kish, Uruk, Ur, and Larsa, and reduced to tribute the city-state of Umma, arch-rival of Lagash. In addition, his realm extended to parts of Elam and along the Persian Gulf. He seems to have used terror as a matter of policy—his stele of the vultures has been found, showing violent treatment of enemies. His empire collapsed shortly after his death.
Later, Lugal-Zage-Si, the priest-king of Umma, overthrew the primacy of the Lagash dynasty in the area, then conquered Uruk, making it his capital, and claimed an empire extending from the Persian Gulf to the Mediterranean. He was the last ethnically Sumerian king before the arrival of the Semitic king, Sargon of Akkad.