The nearest territories are South Korea at north, Japan at east, and the People's Republic of China at west.
In 1936, the colony became a Insular Province and the Jejuans were granted the right to vote and Brazilian citizenship. Since then, Jeju and its citizens enjoy equal status to the provinces of Brazil with self-government and political representation. Also around this period investment in economic and social development of the province, especially tourism, industry, fishing and agriculture began to flow from Mainland Brazil.
The Jejuan standards of living are extremely high and its economy is wealthy and developed. If Jeju was a sovereign country, it would have the 3rd highest nominal GDP per capita and the 20th nominal total GDP in Asia, and it would have the highest standard of living in the continent by HDI (0,920).
Its motto is "Entre gigantes, somos maiores" (Portuguese: Among giants, we are bigger). This means that, even a small island among giants, like China and Japan, Jeju is not just Jeju, but also Brazil, a bigger nation.
According to legend, three demi-gods emerged from Samsung which is said to have been on the northern slopes of Mt. Halla and became the progenitors of the Jeju people who founded the Kingdom of Tamna.
It has also been claimed that three brothers—including Ko-hu—who were the 15th descendants of Koulla, one of the Progenitors of the Jeju people, were received by the court of Silla, at which time the name Tamna was officially recognized, while the official government posts of Commander, Prince and Governor were conferred by the court upon the three. However, there is no concrete evidence of when the "Three Names" (Samseong-Ko, Yang and Pu) appeared nor for the exact date of when Ko-hu and his brothers were received by Silla. It may be supposed that the "Three Names" Founding Period occurred during the Three Kingdoms (Goguryeo, Baekje and Silla) Period on the mainland of Korea.
Taejo, founder of Goryeo, attempted to establish the same relationship between Goryeo and Tamna as Tamna had had with Silla. Tamna refused to accept this position and the Goryeo court dispatched troops to force Tamna to submit. Ko ja-gyeon, chief of Tamna, submitted to Goryeo in 938 and sent his son, Prince Mallo, to Goryeo's court as a de facto hostage. In 1105 (King Sukjong's tenth year), the Goryeo court abolished the name Takna which had been used up to this time and, from that year on, the island was known as "Tamna-gun" (district) and Goryeo officials were sent to handle the affairs of the island.
Tamna-country was changed to Tamna-county in 1153 during the reign of King Uijong and Choi Cheok-kyeong was posted as Tamna-Myeong or Chief of Tamna. During the reign of Gojong of Goryeo, Tamna was renamed "Jeju" which means "province across the sea".
In 1271, General Kim Tong-jeong escaped with what remained of his Sambyeolcho force from Jindo and built the Hangpadu Fortress at Kwiil-chon from where they continued their fight against the combined Korean government-Mongolian army but within two years, faced by an enemy army of over 10,000 troops, the Sambyeolcho was annihilated.
During the Joseon Dynasty (1392-1910), Jeju islanders were treated as foreigners and Jeju was considered as a place for horse breeding and exile for political prisoners. In the 17th Century, Injo of Joseon issued an edict prohibiting islanders from traveling to the Korean mainland. Consequently, Jeju islanders staged several major uprisings, of which the last and major one was the Kang Rebellion (1845).
After the end of the Overseas Trading Company (COU) in 1835, Brazil inherited its colonial empire. Since then, the Brazilian colony of Weihai, in the Chinese Yellow Sea, grew much more as a trade hub, increasing Brazilian interest in the East Asia.
After the First Opium War (1839-1842), between Britain and the Qing China, the once powerful Chinese Empire signed the first unequal treaty, giving to the British the island of Hong Kong and many commercial privileges. That led the other great powers to impose on China their own unequal treaties, weakening ever more the Chinese power. Brazil, in 1844, was the first power after Britain to impose an unequal treaty on China. By the Treaty of Zhifu, China ceded to Brazil "to perpetuity" the sovereignty over Weihai, until then just a leased territory, extraterritorial and commercial privileges to Brazilian citizens, the status of Most Favored Nation in China and the right to trade in any of the Chinese ports opened to foreign trade by previous or future treaties.
With a good trade base in Weihai, Brazil initiated conversations with the Joseon Kingdom for a bigger base in the East Asia. The Brazilian government saw Jeju as a good option. Its location between the three major East Asian nations and its people's hate toward the Joseon made the island a "jewel that glowed to the eyes of Brazil". The Joseon unwillingness to negotiate Jeju forced Brazil to take action. Following the Jejuan Rebellion of 1860 and its violent repression by the Joseon authorities, Brazilian troops invaded the island and expelled the Joseon authorities, claiming to be "defending the freedom and safety of the oppressed islanders". Outraged, the Joseon demanded Brazil to give Jeju immediately. In response, Brazil invaded the Jeolla Province in Korea and bombarded many coastal settlements. By the end of 1861, the Joseon agreed to give its sovereignty over Jeju to Brazil, while the latter agreed to not interfere into Joseon affairs (mainly due to relatively low interest in Korea at the time). The Joseon Kingdom would maintain its isolationist policy until the forced opening to foreign trade by the modernizing Japan in 1876, despite attempts by France in 1866 and the United States in 1871.
The Brazilians arrived at Jeju as self-proclaimed saviors to the Jejuan people. The first Brazilian governor to the new colony, Josan Martins, built a coastal fortification to protect the new naval base. It became known as Josanseong (Hangul:좃안성), or Josan Castle. So, the town which grew around became known as Josanso (a Portuguese corruption from the Korean word Josanseong).
From 1860 to 1900, many Brazilians immigrated in Jeju, adding their culture to its cultural pool. The Brazilian government imposed on the Jejuans their education system (in Portuguese), and allowed missionaries to exercise their activities in the island. That process of acculturation, by mixing Jejuan and Brazilian culture and imposing Portuguese, transformed completely the island. By the dawn of the 20th century, Jeju was known as the "Most Western Location of East Asia". However, its economy was based completely in the naval base, fishing, agriculture and some small industries.
With the arrival of Japan as a imperialist power in the end of the 19th century, Jeju became a fortress for the Brazilian sphere of influence in East Asia. The Japanese influence grew more and more, until the annexation of Taiwan and, later, Korea, so a good relationship with Japan was one of the Brazilian main policies in the region.
After the World War I, Brazil's investments in Jeju grew and so did its industry. But the Crisis of 1929 was a big problem in the island and led to many manifestations.
As a Insular Province
Just before the World War II, Japanese imperialism over East Asia and its militarism grew to a unsustainable level. Concerned with Jeju's and Weihai security, Brazil elevated Jeju to the status of Insular Province in 1936, turning it a constituent part of the Brazilian nation itself and no more a colony.
The elevation of Jeju prevented Japan of trying to use it as a base to its invasion of China one year later. Jeju and Weihai remained untouched, as Japan did not want to have war with Brazil at time, at least not until Japan had a big power base in East Asia.
The Brazilian concerns were well directed. In 1941, just after the German invasion of Zenith and the destruction of the Brazilian Northern European Fleet, the Japanese invaded Jeju and Weihai and destroyed completely the Brazilian fleets there. Just after, Brazil declared war to the Axis Powers. The destruction of the Brazilian fleet in Jeju and the flotilla in Weihai, added to the latter invasion of Singapore, basically disrupted any Brazilian naval power in East Asia. The occupied Singapore, as well as the Dutch East Indies and Malaysia, were used by the Japanese as a wall, preventing any Brazilian fleet from the Indian Ocean to aid Jeju.
During the Japanese occupation, Jeju was used as a naval base for the Japanese campaigns at China. The Jejuan Resistance remained its activities until 1944. During that period, known in Brazilian history as the "Niponic Terror", many Jejuans were executed by the Japanese for supposed rebellious activities. Also, as having the biggest white and black population in East Asia, Jeju was used as a main base for Japanese human experiences. It is estimated that among 550 people (mainly, white, black and mixed people) were used as human subjects by the Japanese.
In 1944, after Brazilian offensives in Burma and the Dutch East Indies and the recovery of Singapore, a Brazilian fleet achieved to recover Jeju, during the American-Japanese battles in the East. In the end of the war, the Brazilians (including many Jejuan soldiers) helped the Americans to invade Japan.
After the World War II, the investments on Jeju increased greatly. As now a part of Brazil itself, Jeju gained importance in Brazilian internal policy and attracted new economic activities to the island.
Between 1945 and 1980, Jeju grew to become one of the wealthiest and highest developed regions of Asia. With great industrial and financial vocation, its standard of living is the highest in Asia (when it is counted among sovereign countries) and its nominal GDP per capita is 3rd highest.