In that period Tangun became chief of the tribe succeeding to his father (hwanung). He abolished the primitive political mechanism and set up a power body controlling administration, judicature and army. And he founded his state with Pyongyang as its capital 5,000 years ago and name the state "Joson" (Korea). This country is called Kojoson in the history to be distinguished from "Li Joson" meaning Korea under the rule of Li in the later period. Pyongyang existed as the capital of Kojoson for more than 1,500 years from the time it was set up by Tangun to around the 14th century B.C. Kojoson, a slave-owning state, was ruled by a hereditary king. It had a permanent ruling machine headed by him, laws and advanced ironware culture.

It existed up to 108 B.C., with its name changed into Tangun Joson, late Joson and man Joson. It had slave-owning form of the economy which developed on the basis of bronze processing technology. Agriculture was the main branch of the economy, ploughing was developed and millet, sorghum, foxtail millet, soybean and various other crops were cultivated. Rice cultivation started there. Tangun Joson had its defensive means and a huge standing army from its early period. After founding his state involving vast areas in the northwestern part of Korea, Tangun expanded its territory, uniting its neighboring small kingdoms. Tangun Joson thus demonstrated its might as an ancient power with a vast territory and exerted great influence on the neighboring countries and tribes in all aspects of politics, economy and culture.