evidence: Arunachal Pradesh became an Indian State today: Some interesting facts about the 'Land of the Dawn-Lit Mountains' Arunachal Pradesh, the 'Land of the dawn-lit mountains', became an Indian state 30 years ago, on February 20, 1987. Arunachal Pradesh was established as a state in India on February 20, 1987. Arunachal Pradesh was initially a Union Territory which was carved out of Assam. Arunachal Pradesh was known as the North East Frontier Agency (NEFA) during British India and the Republic of India until 1972. Prime Minister Narendra Modi greeted Arunachal Pradesh on its statehood day today.