Human society began as small groups whose subsistence was hunting and gathering. Up until around 12000 years ago, humans hunted wild game using stone-tipped weapons and gathered naturally occurring grains and other plants. Some changes started to take place around the end of the Paleolithic in the Near East, modern Iraq, Turkey, Egypt and the Levant. The earliest farming attempts occurred at around 11000 BCE in the Levant, with hunter-gatherers experimenting with animal domestication and cultivating wild grains. However, this never really took off, likely from the climate drying out at the end of the Ice Age. Certainly, the next important developments occur in the higher altitude Zagros mountains in Turkey.

During the Neolithic (8000-4000 BCE), we start to see an increase in agriculture and the development of villages. Most of this development occurs in the 'nuclear zone', where it is too cold for plants to develop naturally but not too cold for them to grow with assistance. It is not exactly clear why humans chose to move to agriculture. Modern anthropology tells us that the life of the farmer is much harder than the life of hunter-gathers, who had far more leisure time (around a 10 hour working week). It may have been the result of a population increase in the warming climate that created a food shortage crisis, prompting technological innovation in production.

Now we are getting to the point. Sorry it took so long. Hunter-gather societies were typically nomadic; they use the resources in an area then moved on. Such systems are likely to be egalitarian, with no real concept of property as we understand it. Agriculture changes this because it creates surplus. When there is more food than the population can consume, then it must be stored, and this requires mechanisms of transportation, storage and distribution. It also requires someone to control such measures. Those who end up controlling production gain wealth. Naturally, as the concept of property develops, fear among the wealthy that they might lose control causes the development of power systems by means of institutions, force, or symbols.

So from the Ubaid period, which started in the 6th millennium in southern Mesopotamia and spread to the north around 5000-3800 BCE, we see the development of cities. This is when the real social stratification occurs; there is firstly a differentiation of power, whereby society is split hierarchically and a ruling class emerges; and there is an increasing diversification of roles. Institutions are then needed to keep society integrated, despite the increasingly centralised power structure. The contemporaneous Northern Mesopotamian Halaf culture was certainly more egalitarian before it was overtaken by Ubaid culture. Then in the Uruk period, 3800-3100 BCE, the need of a leader to organise production gave rise to the power of the temple, which controlled food distribution, and the need of a religious ideology to justify the priest-king who led it.

Eventually religious institutions justify the power held by the king and other royalty as being by divine right. With the development of writing we find the first known king, the Egyptian Narmer, ca 3100, who united Egypt.

So to answer your question, the earliest cities, led by a ruling class, can be found in Southern Mesopotamia around 7000 years ago. The earliest kings are found in the Uruk period in the 4th millennium. The first recorded king is Egyptian, closely followed by the Sumerian kings in Mesopotamia.

Sources: Yoffee, Van De Mieroop, Chadwick.

I feel like this question might be better suited to /r/AskAnthropology.