1956 मायथाइयाव बेखौ मोनसे जुथाइ हायुं आवथा बानायनाय जादोंमोन आरो 1972 मायथाइयाव सा-सानजा जायगाफोरनि (दाफामफिन्नाय) आइन, 1971 जों मोनसे आबुं रायजो बानायनाय जादोंमोन।
It was made a Union Territory in 1956, and a fully-fledged State in 1972 by the North-Eastern Areas (Reorganisation) Act, 1971.