Undivided Assam refers to the then undivided greater state of Assam in India soon after the Indian Independence in 1947 till 1963. In addition to the present-day Assam, it included the current states of Arunachal Pradesh, Meghalaya, Nagaland and Mizoram. The capital of this state was Shillong, currently the capital of Meghalaya.
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Undivided Assam Wikipedia(Text) CC BY-SA