The ancient period history of the area is too scanty and fragmentary to give a connected historical account. The archaeological relics of later times discovered in the area do not provide any key to the ancient period of history. It is in the late medieval period marked by the dominance of the Ahoms in the Assam that the history of the area emerges from vague traditions.
A series of invaluable chronicles known as Ahom Buranjis, of the Ahoms who ruled Assam for long six centuries from 1228 A.D to 1826 A.D, bear the important literary evidences to the historical developments of the area. During the rule of Ahom dynasty the Nishis did not pay taxes to the King of Assam but accepted his sovereignty and obeyed some of his commands.

During the rule of Ahom King Sukhampha, Khora Raja (1552-1603) the area was brought under the Ahom administration. In 1614 the Ahom expedition in this area ended in a total defeat of the Ahoms. King Pratap Singha (1603-41) granted the Nishis the right of posa, the right to receive payments from certain specified villages in the foothills, provided they paid annual tribute to the king. Katakis were appointed for this purpose. A number of paiks were engaged in the duars or passes to supply the Nishis certain necessities of life. The Nishis were entitled to receive from every ten houses at foothills, one double cloth, one single cloth, one handkerchief, one dao, ten heads of horned cattle and four seers of salt.

Despite the grant of posa the Nishis could not be prevented from committing raids in the plains of Assam. In 1646, during the reign of Sutyinpha also called Naria Raja (1644-48), a punitive expedition was sent against the Nishis to avenge the outrages committed by them. The expedition failed and a second expedition was undertaken in 1648. This time also the Ahoms were compelled to retreat.

In 1672 the Nishi rose in revolt and refused to pay tribute to the Ahom King. They raided a village called Taiban in the Lakhimpur district and carried off a number of people. The reigning king Udayaditya Singha dispatched a retaliatory force against the Nishis, ignoring the caution of his Prime Minister. The expedition dragged on for long until it ended in failure and heavy loss of lives.

Hostilities between the Ahoms and the Nishis continued until the latter came to the terms during the reign of Rudra Singha (1696-1714), the mighty Ahom king. The Nishis agreed to provide 600 soldiers to the Ahom army. However the peace and friendship did not last long. The Nishis committed a series of raids after the death of King Rudra Sangha. However the Nishis were subdued in 1717during the reign of King Siva Singha (1714-1744) and King Rajeswar Singha (1751-1769) imposed a blocked on the passes leading to the hills. Consequently the Nishis led a delegation to the king and gave him presents and returned the e captives taken previously. But the arrest of the representatives by the king resulted in hostility until the restoration of posa to the Nishis.

During the Moamaria rebellion, which broke out in Assam in1769 and continued till the early part of the next century, the Nishis made a common cause with the rebels in their bid to over throw the Ahom domination. The rebellion died down quietly. After fall of the Ahoms, the Treaty of Yandabo ceded Assam to the British in1826. The British largely followed the Ahoms in regard to Nishis in the nineteenth century. Up to the first decade of twenty century it was the policy of the British to leave the tribes more or less to look after themselves. Under the British government the tradition of collecting posa continued in spite of the government’s effort to discontinue it and make money payments in lieu of it. Since the money had no exchange value in the hills, it was not acceptable to them until 1852. Since then the Nishis stared settling in the plains and started attention to agriculture.

On the night of 12th February 1872, the village of Amtola, a Nishis village settled in plains near Gohpur was attacked and plundered by two hundred Nishis of the hills. The government stopped the payment of posa since then. From the early part of the 20th century the relationship between the Nishis and the government took a new turn.

In 1914 the area was a part of the administrative unit called Western Section of North-East Frontier Tract. In 1919 it was renamed Balipara Frontier Tract. In 1946, the Balipara Frontier Tract was divided, for administrative convenience, into Se LA Sub-Agency and Subansiri Area and in 1954; this Tract was bifurcated into two administrative units known as the Subansiri Frontier Division and the Kameng Frontier Division. In 1965, the Subansiri Frontier Division came to be known as the Subansiri District. In 1987 the Subansiri District was bifurcated into Upper Subansiri District and Lower Subansiri District. The Papum Pare District was curved out of the Lower Subansiri District in 1993.

The first administrative center was opened at Kimin in 1947, at Doimukh and Sagalee in 1949, Naharlogun in 1974, Balijan in1976 and at Mengio in 1979 and Toru and Laiporiang in 1998.The temporary state capital was established in 1974 at Naharlogun and subsequently shifted to Itanagar in 1978.

Till 1974, the administration of the territory was carried out from Shillong, which was then the capital of the state of undivided Assam and later on the capital of Meghalaya state. It was felt that for the rapid development of the territory, the administrator should come near the people and the search for a site for the capital of Arunachal Pradesh started. The choice for capital finally fell on Itanagar, which was a small village. Initially the capital was shifted to Naharlogun and the foundation stone was laid by the then President of India, late V.V Giri on 20th April 1974.The government had defined the area of the capital complex vide its notification thus.