Archaeological evidence of Gojoseon are found in the transition from the Jeulmun pottery to the Mumun pottery around 1500 BC, when groups of semi-sedentary small-scale agriculturalists occupied most of the Korean peninsula. Local bronze production began around the 8th century BC. Modern historians generally believe it developed into a powerful federation or kingdom between 7th and 4th centuries BCE.
The people of Gojoseon were the descendants of migrating Altaic tribes that settled in Manchuria, far eastern China, and the Korean Peninsula. Gojoseon eventually consolidated in lower Manchuria and the Korean Peninsula.
Dangun Wanggeom is the legendary founder of Korea. The oldest existing record of this founding myth appears in the Samguk Yusa, a 13th-century collection of legends and stories. A similar account is found in Jewang Ungi.
The Lord of Heaven Hwanin (환인; 桓因, a name which also appears in Indian Buddhist texts), had a son Hwanung who yearned to live on the earth among the people. Hwanin relented, and Hwanung descended to Mount Taebaek with 3,000 helpers, where he founded a city he named Sinsi (신시; 神市, "City of God" or "Holy City"). Along with his ministers of clouds, rain, and wind, he instituted laws and moral codes and taught the people various arts, medicine, and agriculture.
A tiger and a bear living in a cave prayed to Hwanung that they may become human. Upon hearing their prayers, Hwanung gave them 20 cloves of garlic and a bundle of mugwort, instructing them to eat only this sacred food and remain out of the sunlight for 100 days. The tiger shortly gave up and left the cave, but the bear remained and after 21 days was transformed into a woman.
The bear-woman (Ungnyeo, 웅녀, 熊女) was very grateful and made offerings to Hwanung. She lacked a husband, however, and soon became sad and prayed beneath a Sindansu (신단수; 神檀樹, "Divine Betula") tree to be blessed with a child. Hwanung, moved by her prayers, took her for his wife and soon she gave birth to a son, Dangun Wanggeom (단군 왕검; 檀君王儉).
Gojoseon is said to have been established in 2333 BC, based on the description of the Dongguk Tonggam (1485). The date differs among historical sources, although all of them put it during the mythical Yao's reign (traditional dates: 2357 BC – 2256 BC). Samguk Yusa says Dangun ascended to the throne in the 50th year of the legendary Yao's reign, Sejong Sillok says the first year, and Dongguk Tonggam says the 25th year. Some historians suggested that Gojoseon was founded around 3000BC
Some historians argue that "Dangun" may have been the title of Gojoseon's early leaders. The legitimacy of the Dangun seems to have been derived from the divine lineage of Hwanin, a religious characteristic found in other ancient fortified city-states, such as those of Ancient Greece.
By the 4th century BC, other states with defined political structures developed in the areas of the earlier Bronze Age "walled-town states"; Gojoseon was the most advanced of them in the peninsular region. The city-state expanded by incorporating other neighboring city-states by alliance or military conquest. Thus, a vast confederation of political entities between the Taedong and Liao rivers was formed. As Gojoseon evolved, so did the title and function of the leader, who came to be designated as "king" (Han), in the tradition of the Zhou Dynasty, around the same time as the Yan (燕) leader. Records of that time mention the hostility between the feudal state in Northern China and the "confederated" kingdom of Gojoseon, and notably, a plan to attack the Yan beyond the Liao River frontier. The confrontation led to the decline and eventual downfall of Gojoseon, described in Yan records as "arrogant" and "cruel". But the ancient kingdom also appears as a prosperous Bronze Age civilization, with a complex social structure, including a class of horse-riding warriors who contributed to the development of Gojoseon, particularly the northern expansion into most of the Liaotung basin.
Around 300 BC, Gojoseon lost significant western territory after a war with the Yan state, but this indicates Gojoseon was already a large enough state that could wage war against Yan and survive the loss of 2000 li (800 kilometers) of territory. Gojoseon is thought to have relocated its capital to the Pyongyang region around this time.
According to the school of historians who believe that Gija Joseon coexisted with Gojoseon of Dangun, Gija Joseon was established at the west end of Gojoseon, which is currently around Hebei, Liaoning and southern east of Inner Mongolia, and was later overthrown by Wiman. Thus Emperor Wu of Han’s conquest of Wiman Joseon was in the western part of Gojoseon, formerly ruled by Gija and his descendants.
The records of Gija refer to laws (Beomgeum Paljo, 범금팔조, 犯禁八條) that evidence a hierarchical society and legal protection of private property.
One account relays that King Jun appointed a refugee from Yan, Wiman. Wiman later rebelled in 194 BC, and Jun fled to southern Korean Peninsula. Wiman Joseon was influenced by the Chinese, but was not a Chinese fiefdom. In 109 BC, Wudi of China invaded near the Liao River. Gojoseon fell after over a year of war in 108 BC. It is posited that after this China established the Four Commanderies of Han in the western part of Gojoseon.
The Gojoseon disintegrated by 1st century BC as it gradually lost the control of its former fiefs. As Gojoseon lost control of its confederacy, many smaller states sprang from its former territory, such as Buyeo, Okjeo, Dongye, Guda-guk, Galsa-guk, Gaema-guk, and Hangin-guk. Goguryeo and Baekje evolved from Buyeo.
By the 7th century BC, a Bronze Age material culture, with influences from northeastern China as well as Siberia and Scythian bronze styles, flourishes on the peninsula. Korean bronzes contain a higher percentage of zinc than those of the neighboring bronze cultures. Bronze artifacts, found most frequently in burial sites, consist mainly of swords, spears, daggers, small bells, and mirrors decorated with geometric patterns.
Gojoseon's development seems linked to the adoption of bronze technology. Its singularity finds its most notable expression in the idiosyncratic type of bronze swords, or mandolin-shaped daggers (비파형동검, 琵琶形銅劍). The mandolin-shape dagger is found in the regions of Liaoning, Manchuria down to the Korean peninsula. It suggest the existence of Gojoseon dominions, at least in the area shown on the map. Remarkably, the shape of the "mandolin" dagger of Gojoseon differs significantly from the sword artifacts found in China.
Around the 6th century BC, burnished red wares, made of a fine iron-rich clay and characterized by a smooth, lustrous surface, appear in dolmen tombs, as well as in domestic bowls and cups.
Around 300 BC, iron technology was introduced into Korea from China. Iron was produced locally in the southern part of the peninsula by the second century BC. According to Chinese accounts, iron from the lower Nakdong River valley in the southeast, was valued throughout the peninsula and Japan.
King Jun of Gojoseon is said to have fled to the state of Jin in southern Korean peninsula. Jin developed into the Samhan confederacies, the beginnings of Baekje and Silla, continuing to absorb migration from the north. Goguryeo, Baekje, and Silla gradually grew into the Three Kingdoms of Korea that dominated the entire peninsula by around the 4th century.