Barrion was first settled some 660 years after the Agnon Kingdom's establishment. Although the exact reasoning for the migration to the location is still of some debate, historical sources speak of a great period of drought in other areas of the country around the same time. Barrion is home to the freshwater lake, which would have been a source for irrigation.
However, history also shows that in addition to drought, Agnon had been involved in a war with neighboring Luvenia. Archaeological excavations of deserted villages in other areas of the country show that the residents may have also fled to avoid capture or death. Although it does not provide for much protection, residents from the moutainous areas of Agnon would have been able to build better protection on the flat plain. The Palace of Barrion is hypothesized to have been built on the site of such a fortress.
Barrion was established as the new capital of Agnon (the previous being Pilmela) approximately 90 years later by King Tiberius Invisa. Having just ascended to the throne, the new king, who was the former chief knight for his father Yamos, Tiberius was interested in promoting Agnon as a center of trade with other nations. As Agnon was not heavily involved in such activities up to that time, Tiberius declared that Barrion would be Agnon's key to the world. Though it had a port, not much shipping or travel was done from it. Tiberius used workers to strengthen the port to hold many ships. A new palace, plus many governmental buildings were constructed.
Over the next 750 years, Barrion become famous for its architecture, and for its increasing prominence in the spice trade. Several attempts through the centuries to change the capital again mostly failed, although Queen Lucile Invisa conducted most business from the palace at Pilmela for most of her 10-year reign.
Barrion was the seat of negotiations for the Gilanan Unification Council from 1957-1959, and was the location for the signing of the Treaty of Barrion on July 21, 1959, which established the Republic of Gilana.
During the Great Gilanan War of 2007, Barrion was mostly protected from attack by Veracan forces, due to the protection granted to the city by Parliament. However, several buildings were hit by missiles from Veracan ships. Approximately 30 residents and workers of Barrion were killed in the attacks.