North-Eastern Areas (Reorganisation) Act, 1971
The North-Eastern Areas (Reorganisation) Act, 1971 was a major reform of the boundaries of India's North-East region into States and union territories. Effect of the changes
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 Establishment of the states of Manipur and Tripura. They were Union Territories before. Establishment of the state of Meghalaya. It was an autonomous part of Assam before. Establishment of the Union Territories of Mizoram and Arunachal Pradesh. Reduction of the area of the state of Assam due to the above changes. Allocation of Lok Sabha and Rajya Sabha seats for the newly created territories. Allocation of seats to the Legislative Assemblies of the newly created territories. Creation of separate High Courts for Meghalaya, Manipur and Tripura. Creation of a new, common High Court for the rest of the modified territories

Later Territorial changes
 Following the Mizoram Peace Accord in 1986, Mizoram was given full-statehood in 1987. Arunachal Pradesh was given full statehood in by the State of Arunachal Pradesh Act, 1986. 