Sinkashid ("Sin (the Mesopotamian lunar god) has arrived...", or similar) was king of the city-state Uruk in Mesopotamia during the Old Babylonian period approximately from 1865-1860, and the founder of the Sinkashid Dynasty, the last period of independence for the city.
During the time of the 3rd Dynasty of Ur (a.k.a the Ur III period, ca. 2100-2000 B.C.), the city of Ur controlled an empire stretching across the entire Mesopotamian plain. As all things do, this empire eventually found its end around the turn of the millenium, due at least partly to wars with the Iranian city of Elam and the invasion of nomadic tribes called Amorites, most likely from the West, in Syria and Palestine. The following period, from 2000-1800 B.C., until the rise of Babylon under king Hammurabi, is defined by various city states trying to pick up the pieces by asserting regional control. As in ancient Greece in the 5th century, these nominally independent cities formed loose political and economic alliances, with an inevitably dominant partner. Thus the Sumerian King List, which reached its final form in the Old Babylonian period, describes the shift of power from Ur first to the city of Isin, then to Larsa, before reaching Babylon under Hammurabi, the final triumph of the Babylonian god Marduk.
Around the time when this political dominance was shifting in wars from Isin to Larsa, in the 1860s, Uruk finally managed to break free from control under Isin. Sinkashid describes himself in his inscriptions as "King of Uruk, King of the Amnanum", an Amorite tribe which had settled in Uruk perhaps a few centuries before. In other words, the peoples who had brought about the fall of the Ur III empire were now working actively to rebuild it. His reign is marked by the renovation and reconstruction of the Temples of Ishtar/Inanna in Uruk which had fallen into disrepair in the previous hundred years, and the building of one of the largest Old Babylonian palaces. The so-called Sinkashid Palace dominated the entire western quarter of the city, and was most likely surrounded by a newly built administrative district upon the ruins of its Sumerian predecessors. Perhaps the greatest political action undertaken by Sinkashid was an alliance by marriage with the rising dynasty of Babylon. Until the end of the dynasty in Uruk, we have correspondence indicating mutual mercantile and military support between the two kingdoms.
Sinkashid was followed by his short-lived son, Siniribam (1832-1827), who in turn was followed by his sons Singamil (1826-1824) and Ilumgamil (1823?). Dates for the next kings, Eteja and Anam, are still uncertain, though, as neither seems to have done anything in particular, attempts to address this deficiency have been rather lacking.
Roughly around the year 1816, Anam's son, Irdanene, took the throne. By this time, Larsa had decisively won the power struggle with Isin, and the great king Rim-sin of Larsa, also an Amorite, took to a systematic conquest of his neighbouring city states. Uruk, situated on a natural trade-route to the Persian Gulf, thus controlling trade with the lucrative southern city of Dilmun and the trade with India, was a prime natural target. Thus, in 1810, Irdanene of Uruk was captured in battle, and Uruk became a vassal to Larsa. Two kings, Rimanum and Nabi'ilisu, managed to gasp out a final assertion to the throne in Uruk, until in 1803/2 Rimsin captured the city. Details are uncertain, but the archaeological records of Sinkashid's Palace show that it and the surrounding district were plundered and burned to the ground, after which time nothing was built in the area.
To us, the entire Sinkashid Dynasty seems to be a political fluke; certainly, the city was irrelevant on the Mesopotamian political scene, asserting at most a certain cultural dominance because of its temples to Ishtar. Still, through these 60 years we have inscriptions giving the (ideal) prices of goods in the region which lead us to believe that Uruk underwent a time of great prosperity. Those few who are interested in these sorts of things thus believe that Uruks rise and eventual fall were almost exclusively bound to its role as a middle-man in foreign trade.