从考古发现已经得到的史料来看，从公元前2900年开始，苏美尔城邦进入一个“诸国争霸”的时代。
比较大的城市有埃利都、基什、拉格什、乌鲁克、乌尔和尼普尔。这些城市因水权、贸易道路和游牧民族的进贡等事务进行了几乎一千年的、为时不断的互相争战。考古已经能大致勾勒出当时的历史情况，但是由于考古发现的史料有限，今天人们所知道的那段历史可能仍然是当时实际情况的冰山一角而已。
基什被认为曾经是一个比较强大的城邦，因为后来许多苏美尔君主甚至并没有实际统治过基什，却也自称基什之王。（不过现在也有历史学家认为，这并不足以说明基什曾经称霸，自称基什之王可能有其他的比如宗教方面的原因）最早的可以验证是存在的国王就是基什国王恩美巴拉格西。
后来一些比较强大的城邦是乌鲁克，乌尔，温马，以及拉格什等。
考古学家在拉格什发现了王室的铭文，使得今天的人们得以知道从公元前2500年到公元前2350年之间约一百五十年间的完整的拉格什国王列表，以及相关的史事，也使得拉格什成为苏美尔各城邦中，今天的人们了解的唯一比较完整的城邦.
“约公元前2500年左右，拉格什强大起来，乌尔南什王时，拉格什在苏美尔中称霸，到了安那叶姆王和恩铁美那王时，拉格什征服了不少地方，苏美尔颇有统一的趋势。后来，国王卢加尔安达因治国不善，引起了暴动，一个名叫乌鲁卡基那的人推翻了卢加尔安达的统治，在平民的拥护下，自己登上了王位，并进行了已知人类历史上第一次政治改革运动，试图维护平民的利益。正当拉格什内乱之时，苏美尔各国爆发了大规模的战争，温马王卢加尔扎克西征服拉格什，杀死乌鲁卡基那。血屠全城。乌鲁卡基那在位仅六年，他的改革也因此而废弃。”
温马的祭司国王卢加尔扎克西（Lugal-Zage-Si，公元前2259～公元前2235年）消灭拉格什的王朝，占领乌鲁克，并将它作为他的首都，他自称他的帝国从波斯湾一直蔓延到地中海。
但是闪族的阿卡德国王萨尔贡打败了卢加尔扎克西，俘虏了他，而苏美尔人城邦的历史也就就此结束了。
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.