There is not much information available on the history of Arunachal Pradesh. The earliest recorded history dates back to 16th century AD when Ahom rulers of Assam extended their kingdom to this region. The Ahom rulers had a tradition of not interfering in the affairs of the tribes of this region. Before 1962, the state was known as Northeast Frontier Agency and was constitutionally a part of Assam. Because of its strategic importance, it was administered by the Ministry of External Affairs until 1965 and subsequently by the Ministry of Home Affairs through the governor of Assam. In 1972, Arunachal Pradesh was constituted as a union territory, and, in 1987, it became the 24th state of the Indian Union.