The Principality of Jin is a defunct polity of the Earth Kingdom, which was established in the Yonggan Conquest and was formally disestablished after the Earth Kingdom Civil War of Kyoshi's era, though it had been much reduced in size after the Yonggan conquest dynasty was replaced by the Hao Ting Dynasty. It was mostly located in the modern-day Five Grains Province.
Establishment under the Nara Ascendency
After the Fall of the Ri Dynasty
Earth Kingdom Civil War
Modern Day
The principality was disestablished as an administrative entity early in the Hao Ting renaissance, under the reforms supported by the Avatar Kyoshi. Although the incumbent Earth King bore particular animus toward the Nara Yonggan (who held the title of Prince of Jin), this action was not primarily targeted at them and was part of a larger reform of the feudal system in which many rump fiefs and titles were formally disestablished or consolidated with others.
The Nara in exile continue to use the title of Prince of Jin as a hereditary title. The de jure heir is Aisin Nara Mukushen, but it has been many generations since any of the claimants has even seen the lands of the former principality.