Historically, the Upper Siang District was popularly known as Pemako, a significant part of the Tibet. It is the home of a number of tribes such as Memba, Khamba Idu Mishmi tribe. Interestingly when India got its independence in 1947 after that, Arunachal came under the Part-“B” of the 6th schedule of the Indian Constitution as a part of the state Assam. The area further became a part of the North-East Frontier Agency (NEFA) in the year 1951 and was reconstituted under the NEFA (Administration) Regulation in 1954. As a result scheduled as part of Assam during 1950-65 wherein Abor Hills District was renamed as Siang Frontier Division. In 1965, as per the recommendations mentioned of the Daying Ering Commission when the responsibility of NEFA Administration was shifted to the Ministry of Home Affairs then the Siang Frontier Division was renamed as Siang district. Later, the NEFA recognized as Union Territory by the name, Arunachal Pradesh on 20th January, 1972 and after that the Agency Council was replaced by Pradesh Council which was later converted to Legislative Assembly in the year 1975. Finally, in 1980, the district of Siang was divided into two parts namely East Siang and West Siang districts. The present area of Upper Siang was earlier remained under the East Siang district with its administrative headquarters located at Pasighat. In 1999, Upper Siang was separated from the East Siang district with its administrative headquarters located at Yingkiong.

Geographically, the district has a total area of 6,590 sq. km. and occupies the rank 11th in State and 153th in India on the basis of the size. It lies at 28°31'N latitude, 95°41'E longitude and 1890 m altitude. In the year 2021, there was a total 81.34% forest area of total geographical area. The district is bounded by China and Tibet in the North, East Siang District in the South, Dibang Valley District in the East and West Siang District in the West. The principal rivers that flow through the district are Siang, Yamne and Nyigong. The climate of the district remains pleasant almost throughout the year. Most of its rainfall occurs in the monsoon season. The actual rainfall in the district was 3410.0 mm in the year of 2021-22.

Administratively, the district is divided into 11 sub-districts, 1 town and 112 villages. English is its administrative language. The district came in to existence in the year 1999. It has administrative headquarters located at Yingkiong Town, situated at the distance of 392 kms from the state capital. There are total 2 assembly constituencies in the district namely Tuting-Yingkiong and Mariyang-Geku. Both are the part of Arunachal East Lok Sabha constituency.

Demographically, according to the 2011 census, the district has a total number of 7,186 households with a total population of 35,320 comprising 18,699 are males, and 16,621 are females which leads it to rank 14th in the state and 637 in India. The density of population of the district is 10 (persons per sq km.). The sex ratio is pegged at 889 (females per 1000 males) while the child ratio stands at 946 (females per 1000 males). As per 2011 census the major religions in the district are Christian and Hindu with 15.98% and 14.90% of the total population. The population growth rate during the period of 2001-2011 was 5.87% including 3.56% were males and 8.59% were females. According to 2011 census the principal language in the district is Adi with 73.88%. In the year 2020 the number of live births in the district was 989 out of which 485 were males and 504 were females. In the same year the number of deaths in the district was 76 out of which 56 were males and 20 were females.

Economically, the district is mainly dependent on the agricultural sector. The chief agricultural products in the district are paddy, maize, mille, etc. Orange, pineapple, guava and banana are the main horticultural products of the region. More than half of the populations are engaged in agriculture in order to earn their livelihood. The district has also a massive hydro electric power project. In the year 2021-22 the gross domestic product in the district was Rs. 97,349 lakhs at current price and Rs. 57,934 lakhs at constant prices in the year 2011-2012. The net domestic product in the district during the period 2021-22 was Rs. 86,663 lakh at current price and Rs. 49,762 lakh at constant prices in the year 2011-2012. The Per Capita Income or NDDP, At Factor Cost during the period 2021-22 was Rs. 1,95,695 at current price and Rs. 1,12,368 at constant prices in the year 2011-2012.

Education wise, according to the 2011 census, the district a literacy rate of 59.99% including 66.45% are males and 52.63% are females. The total literate population in the district is 18,195 persons comprising 10,723 are males and 7,472 are females. The total number of illiterates in the district is 17,125 comprising 7,976 are males and 9,149 are females. The district has several educational institutions including schools and colleges such as Government Higher Secondary School and Jawahar Navodaya Vidyalaya.

Gegong Apang, an eminent Indian politician and a member of the Bharatiya Janata Party who has served as the Chief Minister of Arunachal Pradesh in the year 1980 and again appointed as the chief minister in the year 2003. Omak Apang, a veteran Indian politician and the son of Gegong Apang, the former Chief Minister of Arunachal Pradesh who was appointed as the member of Lok Sabha from the Arunachal West in 1998.

The district has several famous historical and religious places to visit. These places are Mariyang-Pekimodi Circuit, Tuting-Gelling Circuit, Yingkiong-Ekodumbing-Riutala Circuit, Yingkiong-Tuting-Dewakota Circuit, Yingkiong-Tuting-Tsitapuri Circuit, Mouling National Wildlife Sanctuary and many more. Every year a huge number of tourists come to this place to enjoy its places of interest.