Hill Areas Department is the administrative Department of the two autonomous Councils i.e. Karbi Anglong Autonomous Council (KAAC) and North Cachar Hills Autonomous Council (NCHAC). Article 244(2) read with the Sixth Scheduled to the Constitution of India provides administration of tribal areas in the States of Assam, Meghalaya, Tripura and Mizoram. 

The Government of India passed a bill in Lok Sabha in the year 1951 and Sri. Rajendra Prasad, His Excellency the President of India assented to the creation of United Mikir and North Cachar Hills District. The district of United Mikir and North Cachar Hills district was bifurcated into two separate districts under banner as "Mikir Hills" and North Cachar Hills district in the year 1970. The Mikir Hill district was again rechristened as "Karbi Anglong District" w.e.f. 14 October 1976 vide Govt. Notification No. TAD/R/115/74/47 Dtd. 14-10-1976. Thus Karbi Anglong came into being as a full fledged separate district in the map of Assam with its Head quarter at Diphu.

On 1 April 1996 the Karbi Anglong District Council was renamed as the Karbi Anglong Autonomous Council [KAAC] by an Act of Parliament by incorporating into the Sixth Schedule in the Constitution (Amendment) Act, 1995 (42 of 1995) of the Constitution of India. Subsequently KAAC was accorded greater autonomy vide Govt. Notification No. HAD.57/95/63-64, dtd. 29.06.1995, by entrusting 30 (thirty) more departments.

North Cachar Hill District Council was set up on 29th April, 1952 and was later renamed as North Cachar Hills Autonomous Council on 13th September, 1995. Subsequently NCHAC was accorded greater autonomy vide Govt. Notification No. HAD.57/95/268-269, dtd. 25.09.1996, by entrusting 30 (thirty) more departments.

Both the Councils i.e. Karbi Anglong Autonomous Council and North Cachar Hills Autonomous Council are constituted and function under the Assam Autonomous Districts (Constitution of District Councils) Rules, 1951 (as amended).