The first ancestors of the tribal groups migrated from Tibet during the
Northwestern parts of this area came under the control of the Monpa kingdom of Monyul, which flourished between 500 B.C. and 600 A.D. This region then came under the loose control of Tibet, especially in the Northern areas.
In 1913-14, the British administrator, Sir Henry McMahon, drew up the 550-mile McMahon Line as the border between British India and Tibet during the Simla Conference, as Britain sought to advance its line of control and establish buffer zones around its colony in South Asia.
The Tibetan and British representatives at the conference agreed to the line, but the Chinese representative refused to accept the line owing to domestic pressures.
The NEFA (North East Frontier Agency) was created in 1954. During the war in 1962 PRC captured most of the NEFA. However, the PRC soon declared victory and voluntarily withdrew back to the McMahon Line and returned Indian prisoners of war in 1963.
Arunachal Pradesh was administered as the North East Frontier Agency (NEFA) until 1972, when it became the Union Territory of Arunachal Pradesh. It was given full statehood in November 1986.