History of Mon District is the epilogue to the culture and the contemporary life at the district and in turn the history of the Mishmis, Singphos, Nagas, Khamptis, Bhutias and the other tribes. Mon District was not brought under the Civil Administration till the year 1948. By the year 1914, the Foreign and Political Department of Government of India, extended the Assam Frontier Tract Regulation of 1880 to the Hills, which were either inhabited or frequented by Abor Tribes, Mishmi Tribe, Singhpo Tribe, Naga Tribe, Khamptis, Bhutias, Akas and Daflas.

It is by this extension, Government of India named the region as the North East Frontier Tract. Hence, the present Mon District was also brought under same government notification. In 1951, the plain portion of Balipara Frontier Tract, Tirap Frontier Tract, Abor Hills District and Mishmi Hills were transferred to the administrative jurisdiction of the Government of Assam. Thereafter, the remaining areas of the said North East Frontier together with the Naga Tribal Area of Tuensang including Mon District were re-named as the North East Frontier Agency. The district was carved out of the Tuensang District (Nagaland) on 21st of December, 1973. Even in the beginning of the 19th Century, a vast tract of land lying between the administered areas of Assam and Myanmar (Burma) was not brought under the Civil Administration by the British. It is by this extension of the aforesaid Regulation, the Government of India brought the area under some administration in 1914 and the area was named as the North East Frontier Tract. Hence, the present Mon District was also brought under same Notification but practically, there was no Civil Administration till 1948.

In 1951, the plains portion of Balipara Frontier Tract, Tirap Frontier Tract, Abor Hills District and Mishmi Hills were transferred to the administrative jurisdiction of the Government of Assam. Thereafter, the remaining areas of the said North East Frontier together with the Naga Tribal Area of Tuensang including the present Mon (District) were re-named as the North East Frontier Agency. The Mon Sub-division under the Tuensang Frontier Division was created and the officer who was first posted, as the Assistant Political Officer was Mr. W.H. Rynjah.

The district was carved out of the Tuensang district (Nagaland) on 21st December 1973. The district was enlarged in 1991 by transferring some villages from the Tuensang district and creating some new administrative circle headquarters at Tobu (head by the Additional Deputy Commissioner), Mopong and Muknyakshu (headed by the Extra Assistant Commissioner each).