About when did city states develop in Sumer (in B. C. E)

When multiple states were conquered which were far from each other, to make control effective, the Sumerian city - states were developed.

Explanation:

Due to lack of transportation and technologies at that time, it was challenging to run a larger empire. Due to the larger area, the control was limited to a limited area, especially cities.

Leaders like Sargon of Akkad were able to conquer multiple city states. Also, they gathered multiple bureaucracies and used them to administer the conquered city states. Thus, in such way the city states started to develop in Summer.