In 1989 territory was transferred from West Siang district to East Siang. A decade later, in 1999, the district was bifurcated to make Upper Siang district. East Siang district has a long ancient history related with the Chutiya Kingdom. It was probably under Chutiya chieftain rule from a long time, and came under Birpal’s rule in the 12th century.
There are 3 Arunachal Pradesh Legislative Assembly constituencies located in this district: Pasighat West, Pasighat East, and Mebo. All of these are part of Arunachal East Lok Sabha constituency.