The Warring Period experienced a number of great wars between the seigneurs of separatist regimes. In 238BC, the twenty-two-year-old king of Qin, Zheng brought some politicians and strategists, such as Lisi and Weiliao into his court, and drew the curtain of the uniting war. In 221 BC, the State of Qin dominated the whole country and established for the first time in the Chinese history a united multinational centralized feudal autocratic state. The years of war ended at last. Hereafter Ying Zheng was referred to as the First Emperor .

The unification of the county conformed to the tendency of the historical progression and had a positive and boosting influence over the social and economical development.

The city of Ji remained the political, military and economical center though it was transformed from the territorial center of the late State of Yan to a northern city of military importance and a transportation hinge of the Qin Dynasty. The First Emperor of the Qin Dynasty, following the advice of Chamberlain for Law Enforcement Li Si, abolished the subinfeudatory system which had been carried out since the West Zhou Dynasty and initiated a new local administrative system of commandery and prefecture in the whole country to consolidate the feudal regime. According to Commentary to the Luo River of Commentary to the River Classic by Li Daoyuan of the Northern Wei Dynasty, the Qin Dynasty established Guangyang Commandery including Ji city and the area southward of it with the capital in Ji city. And to the north of Guangyang Commandery, five more commanderies were set up in the territory of the late State of Yan along the Great Wall from the west to the east: Shanggu, Yuyang, Youbeiping, Liaoxi and Liaodong. The present Beijing area was formerly part of the following four commanderies--Shanggu, Yuyang, Youbeiping and Guangyang. The city of Ji remained the political, military and economical center though it was transformed from the territorial center of the late State of Yan to a northern city of military importance and a transportation hinge of the Qin Dynasty.